Fantastic Potions and How They Helped Albus Dumbledore in HBP

[felicitys_mind]

Reconciling the death of Albus Dumbledore with Severus Snape's loyalty to him.

On Aug 12, I revised and vastly expanded the essay and changed the title to “Fantastic Potions and How They Helped Albus Dumbledore during HBP”; it was reworked to include excellent comments from readers, to fill in areas that were unclear, to include my latest ideas regarding events on the night of the cave visit (the Felix Culpa Theory), and to integrate other evidence for Good!Snape I was going to use in a separate essay.

On Aug 29, I expanded the background to the Stoppered Death theory to explain how the theory was introduced on the summer 2005 BNU HBP class.  To make room, I moved the AK section to a separate post.

The Avada Kedavra was Real and Instantly Ended Dumbledore's Time on Earth

Need convincing?  Follow the link:  http://felicitys-mind.livejournal.com/3621.html

The Stoppered Death Theory

Theories involving Snape's claimed ability to make a potion able to "even stopper death" were in play before the release of HBP as readers, prompted by a challenge from JK Rowling, tried to figure out how Voldemort was able to survive the backfired killing curse at Godric’s Hollow. One theorist posited Snape as the expert who had brewed a potion for Voldemort that prevented him from dying (http://www.mugglenet.com/search/index.php). With the publication of HBP, readers learned that Horcruxes were actually the answer to Voldemort’s survival; that clever theoriest was on the “Stoppered Death” trail but had the wrong recipient for Snape’s fantastic potion.

Textual clues strongly point to Albus Dumbledore during HBP as the recipient of the potion able to stopper death, so I have confidence in The Leaky Cauldron's Cathy Liesner's Stoppered Death Theory that the curse on the Peverell ring was lethal, but Snape was able to “stopper,” or temporarily postpone, Dumbledore’s death. Cathy was co-moderator with John Granger (Looking for God in Harry Potter) of the Barnes & Noble University HBP online class in summer 2005. Cathy and others had noticed a number of references in HBP pointing to Snape's first potions class in PS/SS.

In the wee hours of August 7, Cathy posted the following at BNU with the subject title “Stoppered Death”:

"I was responding to someone at the Leaky Forum who was sure that Dumbledore was not dead, that somehow the Dumbledore we saw on the tower was only partly there and some portion of him had been preserved in order to return. I personally feel that would be horribly out of character for Dumbledore who had said "After all, to the well-organized mind, death is but the next great adventure." (SS17)

But what occurred to me was that on the tower, while offering protection to Draco from the Dark side, Dumbledore said, "He cannot kill you if you are already dead."

Back before the start of term, Dumbledore destroyed the ring Horcrux...and almost died: "Had it not been--forgive me the lack of seemly modesty--for my own prodigious skill, and for Professor Snape's timely action when I returned to Hogwarts, desperately injured, I might not have lived to tell the tale..."(HBP 23)

Snape's intervention? Could it possibly be related to this: "...I can teach you how to bottle fame, brew glory, even stopper death..." (SS8)

Could it be that Dumbledore had been a walking dead man since the ring Horcrux had been destroyed? He spent the entire book putting his affairs in order, getting Harry ready to take on the challenge before him. Could it be that rather than "murdering" Dumbledore, Snape released the stopper he'd placed on DD's death and allowed him to die?

True, Snape used the Avada Kedavra, but I believe it was to maintain his place inside the Death Eaters...a position that, I believe, will somehow prove crucial for Harry's triumph. Snape is not a murderer...he'd merely postponed DD's death.

What do you think? Is there anything to this theory?”

Two hours later, responding to a comment to her theory, she wrote:

“When I originally read Snape's quote, I assumed he was referring to poison, and thought it disturbing he would offer to share his abilities in poisonmaking to his class! It was the movie's misquote about "putting a stopper to death" that changed my impression to stopping the flow of life from the body, keeping death away by keeping life locked in. DD's hand was withered and black made me think of the use of a tourniquet...keeping death from flowing from the point of entry the way you would prevent venom from flowing to the heart. (Of course, the curse could have been venom-related, for that matter.)

And as is suggested by your "nick" comment, perhaps the potion in the basin wasn't even that deadly, but weakened as he was, it caused the "stopper" to be removed and reinitiated his dying.”

Many BNU readers quickly responded with praise, supporting textual evidence, and explication for Cathy’s Stoppered Death theory. Good!Snape readers were exultant to have a theory that vindicated Snape’s actions on the Tower, and they posted observations that the Stoppered Death theory explained how Snape could cast the AK without murdering an innocent man, why Dumbledore would suddenly visit the Dursleys and take them to account, why Dumbledore seemed to be putting his affairs in order throughout the book, how Dumbledore and Snape seemed to have made plans for Dumbledore’s death, how Snape seems to have surprising skill and aptitude for the healing arts (as when he healed the curse on Katie Bell), why Dumbledore was giving Harry personal lessons, why Dumbledore suddenly gave Snape the DADA position, why Dumbledore trusted Snape, why Dumbledore pleaded with Snape on the Tower, how Dumbledore may have planned to give up his life to save Snape and Draco, how Dumbledore’s sacrifice benefits Harry by enabling Snape to work closely with Voldemort and strengthens Snape’s position, and how Fawkes may well be the means by which Harry is convinced of Snape’s loyalty to Dumbledore.  The archive is no longer online (I got a copy of the files from a BNU "saver"), but BNU member Janet Batchler returned from vacation to read the discussion of Cathy’s elegant theory and was so impressed she left a comment on the thread at 2AM on August 18 that became the basis of a blogpost summarizing the main points of the theory as discussed on Cathy's thread up through the time of Janet's own "Stoppered Death" thread comment: http://quoththemaven.blogspot.com/2005/08/stoppered-death.html.

Cathy Liesner’s BNU co-moderator, John Granger, was quick to congratulate her for cracking the code and posted an essay at 6PM on August 18 about why HBP was the best HP novel that included a section on Cathy’s theory. He gathered much of the supporting evidence on the Stoppered Death thread and expounded it in the context of the larger story; he also expanded the textual support for the theory with additional evidence he had noticed, such as Snape's question about the difference between an Inferius and a ghost (Albus, who is between the two), Snape's willingness to make the UV, Snape’s rage at being called a coward, and other textual support that I don’t have in my essay. Unfortunately, John’s HBP essay is no longer online, but he is expanding his elucidation of Cathy’s Stoppered Death theory for a book he plans to publish soon (hint!). http://www.hogwartsprofessor.com/home.php.

As noted, I'm convinced that Cathy Liesner figured out the theory that explains most of the action in HBP. I'm delighted to have heard of her theory and thrilled to share it with HP fans along with my own "Stoppered Death" developments.  I'm not sure if I'll be right, but I'm sure Cathy Liesner will be.

What’s gives support to the Stoppered Death theory?

The idea of temporarily extending life beyond its natural end was foreshadowed in PS/SS with the Elixir of Life when Nicholas Flamel destroyed the Philosopher’s Stone, but he and Perenell used some stored Elixir of Life to set their affairs in order before dying, which is a parallel to the Stoppered Death potion Dumbledore took at the beginning of HBP and his reasons for taking it.

HBP is about fantastic potions and Potions Masters. The book title refers to Severus Snape, Potions Master. Hogwarts had a new Potions Master. Harry used the annotated textbook of a potions genius, who turned out to be Severus Snape, who was a classmate of Lily Potter, who, in a bombshell disclosure, was described as a potions whiz. There are at least two direct references in the HBP text to “Snape's first potions class”; there are references to the Draught of Living Death and bezoars, both of which Snape discussed in that first class, in a chapter titled "The Potions Master." Rowling clearly set out anvil-sized hints for us to go back to that first class, and when we do, we find Snape's lyrical speech in which he claimed to be able to make a potion that could "even stopper death."

Moreover, there are many references to Inferi throughout HBP: they were mentioned in the MoM security leaflet Harry had on Privet Drive, Dumbledore defined Inferi to Harry on the way to see Slughorn, Snape showed a picture of a corpse attacked by an Inferius to his first DADA class, a student asked a question about Inferi, Mundungus was impersonating an Inferius during a burglary, Snape discussed the difference between a ghost and an Inferi with his DADA students, the lake in the sea cave was full of Inferi, Harry imagined seeing Inferi in Hogsmeade, the merpeople at Dumbledore's funeral reminded Harry of Inferi, etc.

It's important to the theory, I think, that Harry's information about Inferi came from Dumbledore and Snape, the two people in HBP who knew about Dumbledore's condition.  When Snape asked Harry in his DADA class to tell him the difference between a ghost and an Inferius, the answer was “Albus Dumbledore. In Snape’s question, there is a link to PoA, when Snape, covering DADA for Lupin, asked the class how to distinguish between the werewolf and the true wolf. Just as Snape had given a hint about Lupin’s condition in PoA, Snape was giving a hint about Dumbledore’s condition in HBP.  And in both examples, Snape was providing a "master potion" to each man since Lupin himself described the potion as "very difficult to brew" (OP18).  And in another link to "Potions Masters," we learned from Potions Master Horace Slughorn that the Wolfsbane Potion Snape made for Lupin was invented by a wizard named Damocles who had been a student of Slughorn (just as Snape had).

The frequent references to Snape’s first potions class in PS; the frequent references to Inferi, Dumbledore's definition to Harry and Snape's question about the difference between an Inferius and a ghost, and Dumbledore’s statement to Draco on the Tower that “He cannot kill you if you are already dead” are very deliberate clues unified through the Stoppered Death theory.

Canon supports the idea that the curse on the Peverell ring in July 1996 nearly ended Dumbledore's time among the living. When he visited the Dursleys, his wand hand was blackened and “dead-looking.” When Hermione saw the hand at the start of term feast, she said “"But there are some injuries you can't cure . . . old curses . . . and there are poisons without antidotes. . . ." (HBP8) Hermione is a source of reliable information and often foreshadows events, so that was a clue that Dumbledore's hand had been damaged by a deadly curse, and indeed, he later confirmed that a terrible curse upon the Peverell ring had damaged his hand, and if not for his own prodigious skill and Snape’s timely actions, he would not have lived to tell the tale.

How do you stopper a death?

While there is no canon to explain what a Stoppered Death potion does, the original use of the word “stopper” was a “stopper knot” that creates a bulge on the bitter end of a line to prevent it from escaping through a fitting. A similar term mentioned by an anonymous commentator is a stopper used in an old-fashioned hand spinner that stops the thread from falling off the spool and unraveling. In the context of a potion that can “stop death,” these examples call to mind the Fates, goddesses of Greek mythology, who control a person’s destiny by spinning, measuring, and cutting the Thread of Life, and call to mind Severus Snape as both the spinner of Spinner’s End and the Potions Master able to “even stopper death.” So perhaps stoppering a death is figuratively like a tying a stopper knot to the bitter end of the “Thread of Life” as it rapidly reaches the end of its length; death (the separation of body from spirit) would result if the thread escaped.

My guess for two components of the Stoppered Death potion are 1) phoenix tears for their healing properties and the phoenix's ability to regenerate itself and 2) unicorn hair because of its exceptional strength and ability to bind. These ingredients work perfectly with the idea of the stopper knot if the unicorn hair forms the figurative knot preventing the Thread of Life from escaping while the phoenix tears cause the last moment of life to be continuously regenerated. It is in this way that we see a drinking, walking, talking, thinking, vital Dumbledore in HBP even though, because his last moment was being continuously regenerated, he technically had died.

Could magic do that? We know Fawkes regenerates regularly, and we’ve seen an example in the Department of Mysteries of an action in time repeating in a continuous loop; tellingly, the hummingbird is in the Time Room, surrounded by clocks and where the Time Turners were kept. The hummingbird under the bell jar is endlessly re-hatched and re-shelled, yet it never completes its life cycle:

“Drifting along in the sparkling current inside was a tiny, jewel-bright egg. As it rose in the jar, it cracked open and a hummingbird emerged, which was carried to the very top of the jar, but as it fell on the draft, its feathers became bedraggled and damp again, and by the time it had been borne back to the bottom of the jar, it had been enclosed once more in its egg.” OP34

Phoenix tears and unicorn hair seem right as Stoppered Death ingredients because of the contrast to the snake venom and unicorn blood potion that Babymort used to keep himself alive for a year in GoF. Nagini's venom dissolved Arthur’s stitches, and the healers at St. Mungo’s had to give him blood-replenishing potions until they could find a way to heal him; drinking unicorn blood will keep someone alive who is near death, but the cost of killing a pure and defenseless animal is that the drinker will lead a cursed life. In contrast, Fawkes's tears magically heal fatal wounds, even wounds made by venomous basilisk fangs, and unicorn hair is a powerful binding ingredient freely gathered where unicorns shed it in the forest.

The difference between these potions encapsulates the differences between Dumbledore and Voldemort in terms of what they will do, under what conditions, to magically extend life. Dumbledore will not take an action that requires killing or coercing a creature to provide potion ingredients; Voldemort does both. Dumbledore seeks a temporary extension in order to make the WW better and freer before he moves on to the "next great adventure"; Voldemort seeks control over the WW and fears death. Dumbledore’s solution is to keep his body and spirit held together through white magic; Voldemort’s is to tear his apart through dark magic in the hope of achieving immortality.

I’m guessing the Stoppered Death potion is almost unknown and unobtainable due to the need for phoenix tears to make it. After all, phoenixes are rare creatures that are virtually impossible to domesticate. Their tail feathers can be collected in the mountaintops where they dwell, but their tears would only be accessible from a phoenix that had become the companion of a wizard as Fawkes had with Dumbledore. The fact that Dumbledore’s hand couldn’t be directly healed by Fawkes's tears tells me the curse on the ring was extremely dark magic even if its effects weren’t instantaneously lethal. And perhaps phoenixes don’t cry on demand but need to produce tears in the required quantity relative to the immediate need of the person the phoenix wants to heal, so the potion couldn’t be prepared ahead. Dumbledore had to return to Hogwarts after being wounded by the curse on the Peverell ring was so Snape could concoct the potion with Fawkes’s tears. Dumbledore destroyed the ring in July, so Snape should have been back at his Spinner's End house; since he was at Hogwarts, he must have been waiting at the school at Dumbledore's request "just in case."

The beauty of the “Stoppered Death” Theory . . . is that it explains
 

• why Snape was willing to make the Unbreakable Vow with Narcissa (because he knew Dumbledore would not live more than a year and he could possibly hold Draco back long enough for the stopper to come out of Dumbledore’s death, which would neutralize the UV, and perhaps in the hope that Draco would confide in him if he made the UV with Narcissa),
• why Dumbledore made an unusual visit to the Dursleys (to reproach them for their treatment of Harry over the prior 15 years and inform them (and Harry) that Harry will need to visit one more time before his 17th birthday (because he wouldn’t be alive at the end of the year to tell them),
• why Dumbledore was in a rush to give Harry information and to push Harry to get the Horcrux memory from Slughorn (because Dumbledore didn’t have long to live),
• why Dumbledore gave Snape the DADA job in HBP (because Dumbledore knew he wouldn’t live to the next school year, and if they worked it carefully, they could save Draco and protect Snape from the UV by buying enough time for Dumbledore to die from the potion wearing off and let Snape take credit for killing Dumbledore),
• the meaning of the conversation Hagrid overheard when Snape told Dumbledore that he took too much for granted and maybe he didn’t want to do it anymore (in other words, Snape was saying he would rather die from the Unbreakable Vow than unstopper Dumbledore’s death while the potion was still working),
• why Dumbledore wanted Snape to unstopper his death if necessary (Dumbledore knew Draco was assigned to kill him during the school year of HBP and that Snape had made an Unbreakable Vow to kill Dumbledore if Draco couldn’t manage it. So Dumbledore, in order to save Draco from becoming a murderer and to keep Snape alive to help destroy Voldemort from within the inner circle, made Snape agree to fulfill the Unbreakable Vow and unstopper Dumbledore’s death if it came to that point),
• why Dumbledore made Harry promise to keep forcing him to drink the lethal poison in the cave even though Dumbledore had already said it would kill the person who drank it (because Dumbledore was already dead, so Harry wasn’t killing him at all),
• why Dumbledore was pleading with Severus on the Astronomy Tower (he was asking Snape to unstopper his death even though Snape had told him he didn’t want to do it in the conversation overheard by Hagrid, etc.),
• the meaning of the "revulsion and hatred" on Snape's face when he was about to pull the stopper out (because he hated what he was doing. Snape and Harry were described in similar terms in the act of harming Dumbledore ("Harry hated himself and was repulsed by having to force the last of the poison into Dumbledore.") The difference is that we were being told what Harry was thinking without being given a description of Harry's face whereas we were given a description of Snape's face without being told what Snape was thinking.),
• how Snape was able to AK Dumbledore on the tower without committing murder (since Dumbledore was already dead. What Snape did was unstopper Dumbledore’s actual death and allowed it to proceed. That is why Dumbledore could morally ask Snape to AK him and why Snape could morally comply), and
• why Snape was so enraged when Harry called him a coward for killing Dumbledore even though Snape had not been enraged when Harry called him a coward for refusing to fight w only a few moments earlier (because it wasn’t cowardly of Snape to throw the AK at Dumbledore, nor was it murder: it was a wrenching act that he did to fulfill the agreement he made with Dumbledore).

Why would Dumbledore stopper his death?

Dumbledore said “to the well-organized mind, death is but the next great adventure,” so he wasn’t afraid of death. But would Dumbledore’s mind have been calm and settled if faced with imminent death from the ring curse if that meant leaving Harry without the knowledge of Voldemort’s Horcruxes that Harry needed in order to destroy Voldemort? I think not. I fully believe Dumbledore availed himself of a non-dark option like Stoppered Death to buy himself time to educate and train Harry. After all, Dumbledore knew the prophesy and knew Harry was the WW’s only hope of vanquishing Voldemort. That was Dumbledore’s goal as well, and he wanted to assist Harry, especially in sparing Harry by destroying as many as he could himself. Had the real Horcrux been in the cave, Dumbledore would have managed to destroy two that were protected with magic that couldn't be neutralized with counterspells or antidotes.

Moreover, Dumbledore was Flamel’s partner in alchemy, an active participant in alchemical research even if he hadn’t taken the Elixir of Life himself. Nicholas was 660 years old or so, and Dumbledore was still living his natural life at 150, so we don’t know if Dumbledore would have taken some Elixir in the future. He never implied that the Flamels were taking the Elixir because they didn’t have well-organized minds or were afraid of death, and there is no inherent contradiction between choosing to extend your life to do important work and regarding death as the next great adventure. Flamel was the only known maker of the Philosopher’s Stone and therefore the most brilliant alchemist ever born, so his reason for using the Elixir must have been to continue his work. Likewise, Dumbledore was in a unique position--because of the knowledge he had amassed of Voldemort’s personal history--to educate and train Harry in the strategy necessary to defeat Voldemort. Once Dumbledore had done all he could in that Stoppered Death year (by directly training Harry and perhaps archiving more information to leave to him), he would move on.

How did the Stoppered Death potion influence events in HBP?

Knowing that Dumbledore was on borrowed time and knowing that Draco had to kill Dumbledore by the end of the school year or be killed himself, Dumbledore and Snape tried to run out the clock during HBP by thwarting Draco’s attempt to kill Dumbledore (Snape was putting Crabbe and Goyle in detention to slow Draco down and trying to persuade Draco to confide in him). If Dumbledore and Snape could get to the point at which the Stoppered Death potion simply wore off and Dumbledore died from the delayed curse on the ring, then Draco would be off the hook and the Unbreakable Vow would be neutralized. However, if Draco succeeded in pulling something off before the Stoppered Death potion wore off, then Snape would step in and appear to kill Dumbledore and try to save Draco from the dark side.

Why did Dumbledore call Harry during a school night to make the trip to the cave since Dumbledore told Harry a month earlier he believed he had found another Horcrux?  Dumbledore knew the protections on the Horcrux in the cave would be as deadly as the curse on the ring and that his time among the living would come to an end from the retrieval of that Horcrux.  So Dumbledore put off the trip to the cave as long as possible and used the time to track down other Horcrux clues, then when he realized from signs and symptoms that the “stopper” was loosening (just as Harry felt the Felix wearing off a few chapters earlier), he sent for Harry. The trip to the cave took place in late May, which would have been eleven months into the Stoppered Death potion and three weeks before the end of term. Dumbledore allowed Harry to accompany him because he wanted Harry to know how dangerously the Horcruxes were protected and also to have Harry with him to take the Horcrux in the event that he didn’t make it out of the cave.

Dumbledore didn’t know what he would find in the cave, but he knew the protections would be lethal and would hasten the expiration of the Stoppered Death potion if not kill him outright.  Again, when Hermione saw Dumbledore’s hand at the start of term feast in September, she said “"But there are some injuries you can't cure . . . old curses . . . and there are poisons without antidotes. . . ." (HBP8)  Dumbledore confirmed that a terrible curse upon the ring had damaged his hand, so we should consider that a hint that we were going to see a poison that had no antidote. The poisoned mead did have an antidote, so the poison in the cave must not have. Dumbledore said the poison in the cave wouldn’t kill right away because Voldemort would want to question the person who took the Horcrux. Would Voldemort go to all the trouble to make the cave Horcrux as difficult to reach and obtain as he did only to use a poison that could be neutralized with a bezoar or antidote? No. And Dumbledore knew Voldemort would use protections and traps that couldn't be foiled or couldn't be easily worked out.

Felix Felicis and Felix Culpa

Many people are trying to figure out two questions in particular about the night of Dumbledore's death.  1) Why did Dumbledore send Harry to his dormitory to get his Invisibility Cloak before they set out to for the cave since he had ordered Harry to have it with him at all times in the castle and since Harry did have with him in Dumbledore's office?   Dumbledore was ready to go with his cloak over his arm, so why didn't he ask him if he had it so the two of them could just leave?  2)  How is it that the DE raid happened on the very night Dumbledore and Harry made their trip to the sea cave? Was it just coincidence? Was Dumbledore set up? Did Dumbledore set it up himself?

I believe the answer to both questions is that Dumbledore took a swig of Felix Felicis before sending the note to Harry on the night they went to the cave. (Rereading a HogPro thread, I realized it was Professor_Mum, who said she wouldn't be surprised if Dumbledore had taken some Felix to help in the cave for Harry's benefit and if "Oho!" wasn’t a clue that Slughorn was standing in for Dumbledore, it likely indicated a "Slughorn-influenced DD.") The idea that we were seeing Felixed!Dumbledore in the cave seemed right when I read it, and I realized later that it could be used to explain the five minutes Dumbledore gave to Harry to get his Invisibility Cloak. Observations left by readers Meep and Rogueravenclaw (comments below) made me see there is much more to the theory, however, since it neatly explains how numerous important plot threads came together that night.  As Meep noted in her astute comment, "We've seen with Harry's use of Felix that "unconscious" objectives can be met by the potion, even if on the periphery."

Moreover, I expect Rowling, the classics major who loves a twist, is playing on the idea of the felix culpa, or “fortunate fall.”  In a literary context, "felix culpa" describes a series of disastrous events that eventually lead to a happier outcome.

As we saw when Harry took Felix to get the Horcrux memory, Felix does not predict or control other people or the environment; rather it nudges the user to maximize his or her abilities by reacting to the actions of other people in a step-by-step negotiation on the path toward the goal. And that is why Dumbledore, the greatest wizard of his age, would take a shot of Felix. Dumbledore had been on top of his game when he destroyed the Peverell ring, yet he sustained great damage to his wand hand and was “desperately injured” when he returned to Hogwarts to be patched up by Snape. He had no idea what deadly traps or protections would be in the cave.  With his damaged wand hand, his reflexes were slowed. And he would have Harry alongside him on the trip to the cave so would want the advantage of Felix to help him tweak circumstances in his favor for both their sakes.  It does not diminish Dumbledore’s greatness that he availed himself of "liquid luck."

The first hint to the reader that Dumbledore took Felix that night is in HBP when Harry mused about taking a some Felix to get into the RoR. Hermione talked him out of it:

"Luck can only get you so far, Harry. The situation with Slughorn was different; you always had the ability to persuade him, you just needed to tweak the circumstances a bit. Luck isn't enough to get you through a powerful enchantment, though. Don't go wasting the rest of that potion! You'll need all the luck you can get if Dumbledore takes you along with him . . ." HBP24

Just as Hermione handed us hints about the curse and the antidote-less poison, her statement is a foreshadowing that Felix would play a role in the trip to the cave although ironically, Harry was not taking it himself. Harry benefited from the Felix Dumbledore took and from the Felix he distributed among his friends at Hogwarts; Felix was critical to the night's events from two directions.

Dumbledore’s primary objectives were to retrieve what he hoped would be a Horcrux hidden in the sea cave, leave the school with extra protections, and return with Harry safely to Hogwarts. The influence of Felix wouldn’t have prompted him to abandon the trip because the cave contained a fake Horcrux. He wasn’t 100% certain that the cave contained a Horcrux, but he was certain it was the cave in which Tom Riddle had abused two orphans and he suspected something was in there heavily protected.

When Harry took the Felix in order to get the memory from Slughorn, one of Harry's unconscious objectives was met when Harry, under his Invisibility Cloak, knocked into Ginny, setting off an argument that led to her break-up with Dean, which left Ginny free to form a relationship with Harry. This was not Harry's primary objective that evening and Felix didn't "inform" Harry that something lucky had just happened, but an unconscious objective was met by the potion since Harry wanted Ginny to be his girlfriend. In this same way, Dumbledore's unconscious objectives were being met that night even without his realizing it.

On the night Dumbledore took the trip to the cave, he asked McGonagall and Flitwick to patrol in his absence "just in case," and asked Order members Remus Lupin and Bill Weasley to join them, which is evidence that Dumbledore intended to make the trip to the cave well before he sent the note to Harry since Bill and Remus had not been seen at the school during HBP.

Under the influence of Felix, Dumbledore was prompted to give Harry five minutes to get his Invisibility Cloak even though he had reason to believe Harry had the cloak with him. Dumbledore would not have understood why this was a good idea any more than Harry had understood why he should take a detour past the vegetable patch on his way to Hagrid’s, but the five minutes gave Harry time to give instructions, the Marauder's Map, and his remaining Felix to his friends, actions that would prove critical to the night’s events. I initially thought the five minutes Felixed!Dumbledore's gave Harry was lucky in the sense that it allowed Harry to give instructions and Felix to his friends "just in case," which enabled them to know that Draco brought DE's into the school and kept the students alive during the fight. This would have been a conscious objective served since Dumbledore wanted the school protected that night and left a small patrol of his own "just in case." It was Meep who made me see that Dumbledore's unconscious objects were also being served with the "five minutes," since the Felixed!students made the difference in holding back the DE's long enough to let Dumbledore talk to Draco alone and to let Snape reach the Tower in time.

Draco was celebrating the repaired Vanishing Cabinet at around 8:45 PM when Harry received the note from Dumbledore, so Dumbledore hadn’t planned the trip to the cave that night to give Draco an opportunity to stage a DE raid or because he knew Draco was about to stage one. Dumbledore would not have vacated the school had he known the DE’s would be entering in his absence, and the fact that he didn’t put more teachers on patrol who were at Hogwarts (Hagrid, Slughorn, Sprout, etc.) is evidence that he felt confident with the protections in place. The small patrol he formed before leaving was a precaution because he knew Draco had only a few weeks left and might be getting desperate. I do not believe for a minute that Dumbledore knew Draco would be bringing DE’s into the school that night.

When Dumbledore and Harry left for the cave, Imperiused Rosmerta, throwing some customers out the door, spotted them and reported this information to Draco. What happened with the DE raid and Dark Mark set over the AstronomyTower later that night was opportunistic on Draco’s part. The timeline suggests Draco would have known Dumbledore was in Hogsmeade around 9:00 PM, but Hermione said Flitwick didn’t run into the dungeon for Snape until nearly midnight.  From that, I conclude that a DE raid had been hastily put together once Draco knew Dumbledore would be at the Hog's Head for the evening.  Also, there was no way for Draco and the DE's to know that Dumbledore was far away, incapacitated mentally and physically from the green potion in the cave. Moreover, there was no way for anyone to know whether Dumbledore would be able get back to Hogwarts that night since Harry, an inexperienced Apparator, might have left them both splinched on the coast of England in his first attempt at a side-along Apparation.

As Rogueravenclaw noted in the comments, Rosmerta’s seeing Dumbledore was a catalyst for the night’s actions at the school that realized Dumbledore’s “unconscious” objectives regarding Draco and Snape, so Felix wouldn’t have prompted Dumbledore to seek a different route through Hogsmeade to avoid Rosmerta. Dumbledore needed the events of the night to play out as they did for his unconscious objectives to be met.

The peculiar "five minutes" given to Harry to return to GryffindorTower meant Ron, Ginny, and Neville were positioned outside the RoR, which is how they knew Draco had found a way to let the DE’s into the school. As the students followed Draco, they ran into McGonagall, Flitwick, Lupin, and Bill, who had no idea DE's were in the castle. As Lupin said,

“Luckily,” said Lupin hoarsely, “Ron, Ginny, and Neville ran into us almost immediately and told us what had happened. We found the Death Eaters minutes later, heading in the direction of the Astronomy Tower.” HBP 29

Luckily, indeed. If not for the five minutes Dumbledore gave Harry, the staff wouldn't have known to look for the DE's, Flitwick wouldn't have been sent to get Snape, and ultimately Dumbledore would have been killed by a DE, resulting in Snape's death from the UV. In fact I believe Bellatrix was helping Draco all year and wanted the DE's to back him up precisely so that if Draco failed, at least Snape would die; that's why she had been training Draco in Occlumency--so that Snape would not find out what Draco was doing until it was too late for Snape to save his own life.

As Ginny said, “Harry, if we hadn’t had your Felix potion, I think we’d all have been killed, but everything seemed to just miss us.” (HBP29)  Not only did Harry's remaining Felix enable his friends to live through the fight with the DE's, they were central to supporting McGonagall, Lupin, and Bill in holding the DE's back long enough to realize Dumbledore's unconscious objectives regarding Draco and Snape. Of the four teachers placed on patrol, Flitwick had been stunned before the fight began and Bill went down during the fight; without the Felixed!Students, McGonagall and Lupin would likely have died trying to fight a half-dozen DE's, so the DE's would have been on the Tower before Dumbledore could talk to Draco alone and would have killed Dumbledore before Snape could get there, resulting in Snape's death from the UV.

The influence of Felix explains the halting/intuitive way Dumbledore moved around the cave-seeming not to have been there and yet seeming to know what to do and where to go-and explains how Dumbledore knew that the poison would not kill him right away (just as Felix had “told” Harry that Slughorn wouldn’t remember giving him the Horcrux memory the next day).  There was a direct mention of Felix in the cave scene when Harry wondered if his friends had taken the Felix Felicis he left them with. The exclamation “Oho” Dumbledore used in the cave is a big clue to Dumbledore’s use of Felix that night because it’s an expression Slughorn used three times during Harry's first NEWT potions class. The third and last time Slughorn said "Oho!" in HBP was when he introduced the students to Felix Felicis. At some point, I expect Slughorn to confirm Dumbledore’s use of Felix.

The Horcrux in the cave turned out to be a fake, and Dumbledore's life ended on the AstronomyTower upon his return to the school. This doesn't square with the luck we associate with Felix Felicis, but in the context of the felix culpa or "fortunate fall," the most distressing events of the night---Dumbledore's death and literal fall from the Tower, the fake Horcrux, Bill Weasley's injuries, the undermining of confidence in Dumbledore’s judgment, the escape of Dumbledore's apparent killer and accomplices, etc.---were not the disasters they appeared to be since Dumbledore’s ultimate objective, to vanquish Voldemort, was being furthered. There was a cost, but a relatively minor one when examined closely.

Despite finding the fake locket, it was still an advantage to Harry that Dumbledore went to the cave since if Dumbledore had died before the cave trip, the trio might have identified the cave as a possible Horcrux location and made the trip, quite likely resulting in Harry's death. The message in the locket from RAB is a huge clue for the trio, so they'll be able to realize that the heavy gold locket at 12GP is Slytherin's locket.  Harry will still need to find and destroy the locket Horcrux, but there do not appear to be any necklace-type curses on it since everyone at 12GP handled it and tried to open it without harm to themselves.

Bill Weasley’s disfigurement was not as unlucky as it seemed since he suffered no mortal wounds, he was not turned into a werewolf, and his personality was upbeat; moreover because of his injuries, Molly and Fleur were reconciled by Fleur's demonstration of abiding love for Bill no matter what future he faced, prompting Molly to offer Auntie Muriel’s goblin-made tiara for the wedding, which offer, I believe, will lead to the discovery of the mystery Gryffindor/Ravenclaw Horcrux:
( http://felicitys-mind.livejournal.com/2342.html).

Dumbledore had wanted to talk to Draco all year but knew he couldn't without endangering the boy's life, so in the context of the fortunate fall, Dumbledore was able to speak personally to Draco, to prevent him from becoming a killer, to make him see that turning from dark magic is the right choice, and to assure Draco he trusted Severus Snape.  As a result of his confrontation with Dumbledore,  Draco knows he isn't a killer and doesn't want to be associated with Fenrir Greyback and the DE's. Most importantly, Draco knows that help is available to him through the OotP.  Dumbledore had not known what to do regarding Draco’s task other than take the trip to the cave, which would very likely unstopper his death, allowing Snape to later claim to have killed Dumbledore (just as Snape had taken credit for Sirius's death) and getting Draco off the hook temporarily. However, that scenario wouldn’t have afforded any opportunity to talk to Draco, and if one of the DE's had been forced to kill Dumbledore on the Tower, Snape would have died from the UV, and Draco would not have Snape as a protector when he faced Voldemort for his failure to succeed.  Merlin at MuggleMatters pointed out that Snape did fulfil the UV because he watched over Draco, protected him from harm, and carried out the deed, although Snape fulfilled the UV by preventing Draco from succeeding.

The events of the night saved Snape from death by the UV and made it appear as if Snape killed Dumbledore cold-bloodedly, which will strengthen his credentials with Voldemort.  Even the sense among the Hogwarts staff and Order members that Dumbledore had made a grave mistake in trusting Snape will work to Snape's advantage by removing any lingering doubts Voldemort may have; the MoM officials were at the school that night, so word would have traveled quickly that Snape was considered an unequivocal enemy. Voldemort's increased confidence in Snape will provide an opening for him to clear a path for Harry in some way that he wouldn't have been able to do had Dumbledore merely died that night from the cave poison.  And Snape's soul was not damaged by the AK since Dumbledore was “already dead.”

There was one Felixed moment in the cave that I expect will bring about a Harry-Voldemort confrontation: Harry's blood tribute. Dumbledore said the poison wouldn't kill immediately because Voldemort would want to question the person who emptied that basin.  But how would Voldemort be able to identify the person? The blood tribute. The blood traces left on the wall will be Voldemort's means via magic that will reveal the identity of the wizard who was there. Dumbledore’s blood was left on the outer wall, and Harry's on the inner wall. Voldemort will not think to check the inner wall at first because he has a history of forgetting important things, but at some point he will check. Finding the deceased Dumbledore's blood might lead to close questioning of Snape. Finding Harry's blood will spur Voldemort to rush to his other Horcruxes, two of which I believe are at the school. Harry's and Voldemort's paths will converge at the school, where I believe the secret passageways from Hogwarts to Hogsmeade will be key to reaching and destroying the Hufflepuff Cup and may involve Wormtail's life debt to Harry: http://felicitys-mind.livejournal.com/1383.html 
So as unlucky as the events appeared to be on the surface, the outcomes of that night favor Harry in his quest to destroy the Horcruxes and vanquish Voldemort.  A truly fortunate fall if indeed Felix Felicis is involved as appears.

Hogwarts may not be the location of the final confrontation, however, which I'm beginning to think will happen in the Deparment of Mysteries because of the Veil and Love Room, especially if Voldemort goes there to find a Time-Turner to get his Horcruxes back (and may even be set up to do so in a reversal of OP).  Dumbledore described love as “a force that is at once more wonderful and more terrible than death." And you cannot Apparate or Disapparate in the DoM.

I agree with many others that only Fawkes could convince Harry of Snape's loyalty to Dumbledore and that at some point, the Stoppered Death information will be given to Harry from Snape himself after the intervention of Fawkes convinces Harry that Snape had been loyal to Dumbledore all along.

Further Evidence that Snape is loyal to Dumbledore despite his actions that night

McGonagall sent Flitwick to get Snape, and Flitwick went directly to Snape’s dungeon office, so they all expected Snape to be in his office; clearly Sbape did not know the school would be attacked that night any more than Sprout, Slughorn, and Hagrid did.  He wouldn't have been in his office if he had known about the DE raid because he couldn't have expected Draco would be able to kill Dumbledore, and Draco's failure would kill Snape via the UV.  As Hermione said:

”It was nearly midnight when Professor Flitwick came sprinting down into the dungeons. He was shouting about Death Eaters in the castle, I don’t think he really registered that Luna and I were there at all, he just burst his way into Snape’s office and we heard him saying that Snape had to go back with him and help and then we heard a loud thump and Snape came hurtling out and he saw us and -and-“HBP 29

Snape didn’t know Hermione and Luna were outside his door, so if Snape were loyal to Voldemort, he could have killed Flitwick to get rid of one more wizard willing to fight Voldemort.  But instead of harming Flitwick, Snape stunned him since Snape had not been told that a fight was underway, only that DE's were in the school. When Snape ran out of his office and saw the girls, he told the girls to go into his office and take care of Flitwick.

That is odd given that Snape told the Black sisters Harry was mediocre and had thwarted Voldemort by sheer luck and more talented friends. So why didn’t Snape kill Hermione, the most brilliant of Harry’s helpful, talented friends?  Snape told the DE’s to leave Harry for the Dark Lord, but is it likely Voldemort wanted Harry’s friends spared? A faithful DE would have wanted to kill Luna as well since she had helped thwart the attempt to get the prophesy and her father had published an account of Voldemort’s rebirth, his humiliation when Harry escaped, and the return of his DE’s, whose names were published. There was no one in the dungeon except for Hermione, Luna, Snape, and the stunned Flitwick, and Snape must have known that he would be leaving the school that night for good after unstoppering Dumbledore or else dying from the UV. But he didn’t kill them.

When Snape reached the fight, he ran to the Tower, fulfilled his promise to Dumbledore, then hustled Draco and the DE’s out of the castle, sparing Harry, preventing him from using Unforgivables, and warning him to keep his mind closed and mouth shut (i.e., practice Occlumency and learn nonverbal spell casting).  And as Merlin at Mugglematters.com reminded me, Snape didn't kidnap Harry as he could have.

What's wrong with Dumbledore having Snape just kill him to advance military objectives?

I emphatically believe Dumbledore would never ask Snape or anyone else to commit an act that would irreparably tear his or her soul. It’s not an “out” to say that Snape’s soul was already damaged from his time as a DE. I doubt Dumbledore would see it that way.

I believe the consensus among readers is that killing in self-defense would not tear the soul because it wouldn’t cross the line into a “supreme act of evil.”  But the three Unforgivable Curses (torture, control, death by AK) each earn a life sentence in Azkaban, and, tellingly, there is no death penalty in the Potterverse. It tells me a lot that even DE’s who have committed the Unforgivable Curses in abundance are not put to death. Dumbledore’s friend Alastor Moody, greatest of Aurors, refused to use Unforgivables even when given permission; he brought his DE in alive if possible even though it cost him a leg, an eye, and part of his nose. These things give more credence to the idea that Dumbledore was not “alive” in HBP in the way that, say, Horace Slughorn was alive; because if Dumbledore had been truly alive that night, he would have been instructing Harry and Snape to kill him and that would be a reversal of what Rowling has been telling us about Dumbledore and his values. The only way Dumbledore’s order to Harry to administer the poison and to Snape to cast an AK at him can be reconciled is that he was “already dead” and that Harry and Snape "unstoppered" him.

If Dumbledore and Harry had been allowed to return to Hogwarts without DE interference, I am sure Dumbledore would have died soon afterwards from the combined effects of the ring curse, the Stoppered Death potion wearing off, and the cave poison. But since the DE’s were in the school, the alternate plan had to be worked, with Snape taking over from Draco and at least appearing to kill Dumbledore on the Tower. So Snape unstoppered Dumbledore’s death on the Tower using a real Avada Kedavra curse on Dumbledore’s orders. And since Dumbledore had technically been dead since the previous July, it was not a murder but rather pulling the stopper out of Dumbledore's magically extended life, allowing Dumbledore’s death to proceed.

Given this theory, why did Dumbledore want to see Snape even before knowing about the Dark Mark over the AstronomyTower? Because it was time to commence "Operation Save Draco" by having Snape be in a position to later take credit for killing Dumbledore. Pat over on the HogPro forum also pointed out to me that Dumbledore may have wanted to have a conversation with Snape and Harry together to ask them to put aside their differences and animosity and work together to defeat Voldemort. I think she’s right.

Must read essay: 'Good Snape' is not a 'Square Circle' By H.M. Ketcham
http://www.hogwartsprofessor.com/home.php?page=docs/GoodSnape2