Okay, so I have a rough outline of the real history of how the Nightlands came into existence, and want to lay it out.
The first people to live in the Westerlands were the Quendár, the "Speakers". They considered themselves the first race to speak, but soon started teaching the intelligent animal races language. The Quendár, immortals who could return to life if killed, became guides for other races, guardians for the weaker, and peacekeepers.
The second people to come to the Westerlands were the Kessír, or "Firi Quendár" as the Quendár called them - "Mortal Speakers" or "Mortal Elves", came to view the Quendár with respect, accepting their guidance and mentoring, forming communities of their people around those of the Quendár.
The Quendár came in three peoples, the Forest Folk who were most common, spread across the mainland, the Sea Folk less common, holding seaside villages, islands, and Endánórë, their tropical homeland of old, and the Crafter Folk, the least frequent, living mostly in the Khazad Mountains where they could collaborate with the Stone Folk.
The Kessír came in several peoples, Malda (Gold), Telpín (Silver), Taurë (Wood), Rámar (Winged), Mistá (Grey), Ninquë (White), Oár (Sea), Laicá (Green) and Morin (Black). They found different places to suit them, and Quendár who they got along with best, though some like the Ninquë and Morin preferred to be away from Quendár influence.
In what would become the Days of the Last Sun, the peoples of the Westerlands started to take note of an influx of people migrating from out of the east, across the Khazad Mountains. This exodus was met with curiosity and growing worry as the Quendár started to inquire the reasons of the migrants. They told a tale of a great empire in the east of short-lived people, even shorter-lived than the Kessír. As more migrants came, some of these mentioned people also came and the Elven folk came to call them Quellë Nossë by the Quendár and Pelen Gwaith by the Kessír, both meaning "Fading People" referring to how easily both Elven races could see them age. The Quellë Nossë called themselves "Edan" or "Men".
With the incoming Menfolk, the events in the far east were becoming clearer. Men had a great empire there, slowly expanding and claiming more lands, but a religion had taken hold, gaining the support of a past emperor, that decried all magic as evil, menfolk who used magic as corrupted, magical races as monsters that need to be exterminated. Those who had forewarning fled in the face of this, the Edan magic users as well.
The leaders of the Quendár met, along with the greatest leaders of the Kessír, and the lords of the Dwarrow, the Stone Folk of the Khazad Mountains, in the hall of the Dwarrow High King, and discussed the problem of the Edan empire. Despite disagreements, especially coming from the Dwarrow, they chose to send an envoy to meet the empire, and leading it would be the Crafter King himself.
They had high hopes this would stay the empire and keep them on the eastern side of the mountains. The people they met was an encampment of the imperial army, who on assessing them to have magic, immediately attacked, killing the Crafter King, injuring the Forest Prince, son of the Tauráquendár king, and only by quick action of their dwarven escort, escaped without losing too many more.
The Crafter Prince, firstborn to his father, was of a fiery temperament and took his father's death ill, especially as Quendár priests had informed him that the King refused to return to the living. The Forest King was also offended on his son's behalf, while the dwarrow were pragmatic, saying they had known full well what sort of reception the envoy would receive, having in the past also tried to speak to the imperial peoples.
The Crafter Prince called for war and there was little objection, with what was spoken more a word to not rush into it.
The peoples of the Westerlands made the Khazad Mountains the place they would stand, where they would block the empire's advance. They were the mountains of the dwarrow, who had seen the empire's hate, and the lands westward were the lands of the Elves and refuge of magic creatures. This resistance stood well for some time, but they started to get Edan coming up to attack from the south, where they had crossed the mountains on the southern continent or the land-bridge between it and the north.
This called for a new front in the south, which the migrant Menfolk who had settled in the west chose willingly to defend. This did however reveal another problem, that of the Morin Kessír of the southern lands, vicious folk who chose the distraction of the war to send raids into the north, but the northern Kessír also helped fight them back, alongside the Men of the north.
In the midst of the turmoil, the Crafter Prince witnessed a falling star, and leaving his sons to lead the fight, went in search of it, knowing sky-metal made truly special creations. However when he returned, instead of sky-metal, he came bearing three infant children, girls who seemed to be Quendár in form, but he swore he found them in the crater of the fallen star. He sought out his wife to care for them, having accepted them as his own daughters.
In the safety of the mountains the Three Sisters grew up, war the war fell into a lull briefly punctuated by pushes by the fast-lived, fast-breeding Men. The Sisters were innocent and protected, with the added support of the Dwarrow who were their allies and gave them protected places within the mountain stone. This innocence would be shattered when a force of Edan allied with the Morin Kessír tried to capture the Sisters and take them away. In the attempt younger brothers of the three fell to death and the poisonous magics used to slay them held them back from returning to life.
But this attack also revealed the hidden power of the Sisters, who in turn called up a powerful flame, a Star Fire, which they turned on their attempted abductors, sentencing them to a painful death.
Another problem that started to come to light was the opening of gateways into pocket realms that would become known as the Fae Realm. This arcane Other world was one of far more chaotic magic, existing as it did deep in the reaches of the Arcane, the magical foundations of the world. It's inhabitants showed to have been changed by living in such deep and wild magic, more chaotic than anyone in the mundane world. People who encountered them were subject to their "play" - torment that could be anything from merely tiring and upsetting to absolutely brutal and torturous.
The Quendár were forced to split their attention from the eastern war with the Sun Empire, and find a way to deal with the Fae. Busy as they were with the war they could only give enough time to mark out and contain new gateways found, by ringing them with monuments that kept them contained.
But some of the Fae eventually proved they could be reasonable and allied with the alliance of Westerlands peoples. They were able to start explaining the appearance of the Fae, explaining the the Sun Empire was not only trying to encroach on the Westerlands, but also had traveled across seas to the east, to other lands and conquering there as well, destroying magic there as they found it. In those lands on the far side of the world, a circle of powerful magic users of several races had found a way to open gateways into the Arcane and calve out small worlds to live in, creating the first of the Fae realms. As these realms grew in number, they started to build links and formed a society which they called the Seelie, the Light Court or Summer Court. Another court grew in opposition to them, and the Seelie only spoke of the Unseelie in dread.
The Sun Empire did not remain unaware of the Fae and started trying to close their gates and even trying to destroy fae realms from the inside. In response, the Seelie Court found a way to shift their gates away from lands the empire did not have a hold in, giving rise to their appearance in the Westerlands. The Seelie came to agree to abide by some rules when interacting with people in the mundane world, keeping their actions within the areas immediately around their gates, while mundanes who crosses those areas were putting themselves at willing risk.
The Seelie proved valuable allies in the war, being able to use gates that remained open in imperial lands to spy on the empire and even transport agents into those lands.
It was through these efforts to see behind imperial lines that information was gained about the empire seeking a way to destroy magic. The empire had already succeeded in destroying Fae realms before, and become aware of the Arcane which they existed in. Their researchers thought this could be used to destroy the Arcane all together, ridding the world of all magic.
When this information got back to the leaders of the Westerlands, they were horrified, but it was Losá of the Three Sisters who thought a way could be found to block off the Arcane from imperial lands and keep open access to it in one area of the world - essentially removing magic from the empire and drawing it to the Westerlands. She would head up the research into how to do this, aided by her sisters and some of the greatest sorcerers of the Westerlands.
Their research would prove that the most stable form to do this in would be to cut include a whole section spanning from the north pole to the south, with the polar points acting as anchors. They would need to mark out the eastern and western borders manually, but the Dwarrow High King, Kári, said the dwarves could mark out the border underground, while the Gaearon Kessír - water-dwelling Kessír - and merfolk - semi-humanoid sapient sea creatures - could mark the west,, which would fall in the ocean.
There was some upset when further calculations for this action meant the border would have to cut across Endánórë, but the Lord Captain came to accept that he would have to call his people to the eastern coast of Midland when the ritual was enacted.
The process of preparing would take well over a year, with most of the dwarrow and Gaearon Kessír working hard on laying the markers for the border - powerful crystals that would conduct the energies that would let loose. The West's spies in the Empire kept a close watch on imperial progress on their ritual, knowing that the one to protect Magic and the Westerlands would have to be enacted before the Empire's.
During this time, the war ramped up to a new height, with the Empire attacking steadily. The problems in the south however had calmed somewhat as the distance the imperial forces there had from their masters was weakened by distance, however it did mean they were more prone to Morin Kessír influence as well, taking on a darker aspect as they began to build their own empire.
The Seelie sent out messages across the Fae Realms and more fae gateways were moved into to westerlands as the information that something big was coming that might destroy any gates open anywhere else.
The West's plans were almost complete when a desperate message came from spies on the Empire to say they had started their ritual of destruction. It forced the Three Sisters into action, seeking the aid of a couple of silver dragon allies to transport Losá to the northern pole and Elená to the equatorial mountains, while Elossí was already on her way south, on a ship commanded by a Ëarquendár friend. The only problem was the last point that needed someone on it to channel the spell was seemingly deserted for the night, and Kári used a magic portal to reach the Endánórë mountains.
The Fall of Night was a massive magical undertaking, upset by the destruction spell also being conducted by the empire, and further confused by unknown Fae realms trying to interfere in both. The effects would be titanic, causing massive upheaval of land as new mountains were raised on the eastern border and existing mountains raised higher. Great sea waves caused in the west due to to the raising of islands and the upset of others already existing. The conflict between the two rituals would cause both to go wild but the Three Sisters would eventually gain control over theirs, winning out and keeping magic safe by drawing it away from the destructive spell.
But the intent of the Sisters did not turn out quite as they expected - the lands of the West between the Khazad Mountains and Endánórë became bound in a night than never waned. The sun did not rise, but instead a second, larger moon that would prove to cause random chaos would appear in the sky in the sun's place.
The power of the magics involved cost Kári his life, but his people would swear they could hear him in the Stone.
The cataclysmic effects of the land changing to raise mountains were devastating across the lands, but where the West and South had magic to help them recover, the Sun Empire of the east had none and were left floundering in devastation, which eventually bring their society to collapse.
Elossí had a long though still relatively easy journey by sea to return to the north. Along the way the crew of her ship was able to survey a number of newly emerged islands, which would eventually be colonised by the Ëarquendár and their Calen Kessír allies.
In the effects of the upheaval, Losá's silver dragon ally had been forced to flee on wing to save herself, so Losá had to trek south on her own, but along the way met a tribe of Edan who she stayed with for some years after falling in love with one of their warriors.
Of the three, Elená had the hardest journey home, as she was taken captive by Morin Kessír as she heading out of the mountains. She would be missing for several years and only seen again when she turned up in the fledgling Edan Kingdom on the southern coast of the northern Nightlands, a hardened warrior woman in the company of a man of the southern empire of Men.
Both Losá's husband and Elená's companion seemed to stop aging completely, outliving menfolk, and even Kessír, sustained by their bonds to the Sisters.
Barely a hundred years later the Unseelie would try to invade the north, opening gates in the northern Nightlands. The High Elves and Seelie Court would work together to fight them, with the Seelie attacking from within the Fae Realm, while the High Elves would close the gates of the Unseelie from the outside.
A couple of centuries after this, the Black Empire of the Morin Kessír would try to attack the north, with Unseelie aid. The Empire of Men in the south seemed to be allied to them, but quite a few of their actions seemed to hold the Morin Kessír back, leaving the North confused as to their stance.
These would prove to be the first wars between North and South of the Nightlands, but they were the impetus for the Crafter Elves - now called Star Elves - to completely pull out of the mountain enclaves in the south, handing them over to Tauráquendár - Lómaquendár or Night Elves - hold onto. The Night Elves of the south would become very stubborn about holding the Star Vales, fighting off all attempts by both the Black Empire and Unseelie to claim them with a fierce valor.
Of the Three Sisters once they found their ways home, Elossí would settle in a cluster of islands in the north, held by her trusted Isilmaquendár (Ëarquendár) allies, ending up wedded to her adopted brother, who she had long held non-sisterly feelings for.
Losá would eventually gain news of Elossí, and she and her husband's tribe would settle in a network of seaside caves, creating a port city that Elossí's people would frequently trade with.
Elená and her protector would eventually make their way to the city of the Dwarrow High King, settling in the Star Vale in the mountains over top of it, and linked to it via stone passageways. This would prove the right thing when a young dwarrow prince came to recognise Elená speaking to her with a name only Kári ever called her. Kári had been reborn, in a way somewhat similar to Quendár being reborn, and would continue to return periodically, through the following millennia.
That is a rough outline of Nightlands pre-history, how they really came to exist, and the part the Three Sisters had in it. Most common folk, both Human and Middle Elven, don't know this story. Nightfall is so far back (probably about ten thousand years before Current Era) that the events have become legend and myth. Some vague idea does remain in the stories of ancient magical wars, or Moon Goddess verses Sun God, but they have drifted far off the truth. The High Elves remember, as do the Queens of the two Fae Courts, but in the case of all those groups, they tend to keep the truth to themselves.
I don't have names for all the players involved either, and those I do have tend to be cribbed straight from LotR and RB-verse, as is language, with the Quendár language taking straight from Quenya and Kessír more from Sindarin.