Azeroth
They were aided by a Keeper of the Grove(can't remember his name)
They were aided by Cenarious a demigod. The Keepers of the Gorve are his offspring.
through some sort of massive explosion that resulted in the separation of the former supercontinent into to smaller continents.
They destroyed the Well of Eternity
and Furion cut a deal with the dragons to give them strength to fight off the demons if they should return again. He was sent off in a sort of sleep known as the emerald dream, where he would gather power to fight off the demons again when they return.
It wasn't just him, all the Druids did the same.
(I don't know, I might have skimmed over a few details, but that's the gist of the story from where KrimzonStrider left off. Could somone else steeped in warcraft lore pick up?)
Alright, well first off the Night Elves then decided to use this new well and with the help of Cenarious and the Dragons blessed it with nature and planted a seed within. It would later grow intothe World Tree, granting the Night Elves their immortality and continued magical control over nature.
Now at the same time some of the High-Born left were banished from the Night Elf realm, they took a vial of the water from the Well of Eternity and traveled across the see. They came upon a new continent and named it Quel'Thalas. These are the High Elves. At first due to their lack of magical exposure (unlike the Night Elves who now had the World Tree) they began to lose their dark skin color, and became more peach like. At the same time they decided to forsake the moon held so highly by the Night Elves and embrace the Sun.
They used the vials of Well of Eternity water to create the Sunwell, which granted them their immortality and control over magic. The High Elves then regained their control over magic(but not their immortality. Though they do live 2000 years old O_O) which was just in time because they were forced to wage war agaisnt the Amani(Troll) Empire. They defeated them 3900 years prior to warcraft I. However the trolls were not finished, they prepared for many generations and relaunched their campaign 2200 years before Warcraft I starting the Troll Wars. The Elves were forced to turn to the Human nation of Arathor for help, and with it won the wars crushing the troll empire once and for all.
The high Elves wouldn't be seen by the outside world until the Second War with the horde when orcish forces burned several outlaying elven villages. The High Elves then pledged full support to the alliance and helped crush the Horde. The High Elves would then be a target for the Scourge who were to bring the second coming of the Burning Legion. Prince Arthas(then a Death Knight under the Lich King) led the Scourge on a path of destruction and death stariaght through the middle of Quel'Thalas destroying all opposition and finally the capital city of Silvermoon. Arthas then tainted the Sunwell with demonic powers to ressurect the necromancer Kel'Thuzad as a Lich. Their Ranger general Sylvanis Winrunner was killed and ressurected as the Banshee Queen, and would later manifest the form of a Dark Ranger.
It is estimated 90% of the high elf population was destroyed by the Scourge. At this time Prince Kael'thas decided to accept the demonic powers which the High Elves held as taboo and disgusting, and he found many followers. These became the blood elves who only wish to see revenge in the destruction of their kingdom. He allied homself with the Naga and Illidan and therefore became a pawn of the Burning legion. He and several of his followers left to outland where Illidan and his followers regroup.
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Many Blood Elves decided not to join with Illidan however, and have begun reconstructing their homeland of Quel'Thalas. This has caused much uproar in the High Elf community however as they view the Blood elves as traitors to their own kind and do not wish to see their homeland occupied by them. The high Elves are for the most part powerless due to their diaspora across the planet, mostly to Theremore and to their dwarven allies the Wildhammers.
As such they used their political power to deny the blood elves access into the Alliance and the Blood Elves have thus turned to the Horde creating an uneasy truce with them. The Blood Elves do not mind their relations with the tauren, but are wary of the orcs(due to the second war), and trolls (ancient enemies) and especially the Forsaken(spite towards the destruction of heir homeland). Stil lthe uneasy bond is there.
So theres the history of the high and Blood elves for you.