Some day I'll channel all of this dorky canon essay-ish writing into real essay writing. Or fics. Whichever.
OKAY SO. Because it's been brought up several times and I keep forgetting to talk about it, here we go. Time Lords, if they are on the brink of death, are able to completely regenerate themselves -- in doing so, they are rendered completely different people, although the same drives, motivations, and knowledge remain; however, his or her personality and appearance are completely changed.
But there is some debate on whether or not the Time Lord completely dies in the process -- and it's difficult to tell, because the only regenerations seen on screen are the Doctor's regenerations, in addition to the Master's in New Who season 3, and Romana I into Romana II (which was a bit \(o_O)/ in itself); and the Doctor's regenerations
probably cannot be viewed as the standard.
The Doctor's regenerations, except in one case, are always just before he completely dies. The exception to this is the transition between Seven and Eight, in the 1996 made for TV movie, where Seven is killed and left in a morgue, and regenerates into Eight post-mortum; he had been dead for a few hours, and I believe he states that the anesthetics used in his surgery interfered with his regeneration (I'll need to rewatch this later).
Anyway, here's some TV canon vs. non-TV-canon information on regeneration.
Canon
- Time Lords are able to regenerate twelve times, barring the intervention of the Time Lord Council, allowing for thirteen "selves" [the Doctor I play has regenerated nine times, and is the tenth incarnation]; The Deadly Assassin
- The Time Lord Council can reset a Time Lord's number of regenerations; The Five Doctors
- It is possible to take possession of other bodies in order to extend one's lifespan -- however, the ability to regenerate is then suspended; see the Master (The Keeper of Traken)
- During the regenerative process, a Time Lord's body produces a great deal of energy; The Christmas Invasion
- There is a 15 hour grace period, in which the residual energy from the regeneration process (as mentioned above) is still active in the Time Lord's body, which allows him to continue regenerating; The Christmas Invasion.
- It is possible to completely kill a Time Lord by destroying his body entirely, such as through vapourization; The Deadly Assassin, The Arc of Infinity
- There are weapons on Gallifrey that suspend a Time Lord's ability to regenerate and are able to kill them; The Five Doctors.
- When a Time Lord regenerates, he does not necessarily have to appear human (or Time Lord, to be more specific). It is possible to regenerate and appear as a different species; Destiny of the Daleks (Romana's regeneration), there's also possibly a line about this in the Doctor Who 1996 movie, but I can't remember the exact wording.
- It is possible for a Time Lord to resist the regenerative process; The Last of the Time Lords
- Regenerations do not always go smoothly; immediately after regeneration, it is possible for the Time Lord to experience extreme fluctuations in personality. (Elaborated later)
Non-Canon (fandom, speculations, extended universe [books, audios, etc.])
- It is possible to kill a Time Lord by piercing both hearts at once; The Infinity Doctors, by Lance Parkin
- Time Lords begin life with one heart, but after their first regeneration, they grow their second; fandom.
- Time Ladies have the ability to control their appearance; Time Lords have some degree of control (Utopia, implied with the Master's regeneration)
(LET ME KNOW IF I'VE MISSED ANYTHING.)
Ways the Doctor has Regenerated (a.k.a., ways he's [almost?] died)
- First: An energy drain -- "old age"
- Second: Time Lord Council forced a regeneration as punishment
- Third: Poisoning from radiation from Great One's crystal cave (Planet of the Spiders)
- Fourth: Fell from a radio-telescope tower (called Pharos Project) after disconnecting power power cable to prevent collapse of the universe; required the help of the Watcher (version of himself) to regenerate; post-regeneration, unstable personality; began to take on personalities of former selves
- Fifth: Spectrox toxemia (poisoning from touching raw spectrox); gave companion, Peri, the remedy; post-regeneration, became extremely paranoid and attempted to strangle companion
- Sixth: Died in an attack on the TARDIS by the Rani from unspecified wounds
- Seventh: Shot non-fatally in the chest in San Francisco; killed accidentally by doctors performing surgery; regeneration delayed due to anesthesia; post-regeneration, experienced amnesia from "being dead too long"
- Eighth: Unspecified; believed to have regenerated during Time War
- Ninth: Cellular degeneration due to absorbing energies from time vortex; post-regeneration, became extremely manic and experienced regeneration sickness
ALSO. Jeff (Master-mun) and I are sort of in disagreement over the nature of Time Lord regeneration; namely, whether the number of regenerations is imposed on Time Lords by the Time Lord Council, or if it is a number written into a Time Lord's biology. If it is the former, then the Doctor and the Master would have the ability to regenerate infinitely, because the Time Lord Council has ceased to exist.
Personally, I think it's the latter, while Jeff thinks the former. AGREE TO DISAGREE. ¯\(°_o)/¯ Even so, if asked a question concerning this ICly, I'll probably be trying to be as general as possible to avoid having to retcon too much.