Drow were born from the Demon Spawn War. In this great conflict an army of wood elves under General Lolth found themselves surrounded by three demon armies. Rather than be annihilated, the demon commander met with Lolth and promised safe passage from the field on the condition that her army sit out the rest of the war and that Lolth become their prisoner. Remarkably, the demons stuck to their word but Lolth was to suffer such torture that she broke and became something like her captors. The other wood elves of Morangrel came to calling Lolth's wood elves the Drow - which is a word they use to refer to evil sprites.
The drow were shunned by the other peoples and even by non-evil fey. This led to friction between the two and a series of wars which nearly led to their end. It was during these trying times that some drow took to praying for the return of Lolth. This became the start of her becoming a God. Lolth answered the prayers of her female worshipers, guiding them away from their enemies.
Old scores will be settled later, if not in your generation, than in those that follow. First we must rebuild and expand into areas with weaker competition.
- Lolth, to Brethael 1st Priestess to Lolth - "Into the Deeps"
The drow fled into Kriav's Underdark; and eventually to other worlds by way of feywild fuses. In 411 LE, several hundred drow settlers used one of these rifts to cross over to Bal-Kriav. They re-occupied the ruin Tyelmantar. In Bal-Kriav's Underdark the descendants of this city spread far and wide by way of the Earth Seam and other rivers.
Drow societies where Lolth worship is dominant are almost always matriarchal. They are ruled by the females who are either fanatical or claim to be, in their worship to Lolth.