Start of The Sundering

It is said that a schism in Elvish society facilitated by several Elf nobles drove the Elven Empire to civil war, thus creating the Dark Elves. After this fracture in the seemingly idyllic kingdom of the Elves, other kingdoms and races split into factions and many of these separatists banded together to form an unstoppable wave of destruction; eventually encompassing all the known world with each race and culture in it. Little is known as historical fact but this version of events are universally held as truth. It is unknown who started the war but there is evidence that most, if not all, races lived in harmony prior to the start of The Sundering.

Either tempted by dark powers or, through intervention on behalf of different gods and powerful creatures within the material planes, several "splinter races" were brought into being. Drow, Duergar, Aasimar and Tieflings are to name but a few. These races are echo's of The War in Heaven and the events that lead to their progenitors being created.