Lolth, the Queen of Spiders

Symbol	A black widow spider descending a fine thread
Home Plane	The lower plane of hell (The Demonweb Pits)
Alignment	Chaotic Evil
Domains	Chaos, Evil, Darkness, Demonic, Destruction, Drow, Envy, Lust, Oracle, Pestilence, Pride, Spider, Trickery, Wrath
Favoured Weapon	Dagger

There are a few variations on the mythos of the drow but all of them revolve around lolth's relationship with the other gods of the elven pantheon, long ago when they first arrived on Madius.

One myth says that initially the elves held dominion over the material plane, working in harmony with the fey to tend to the planet, but eventually the other races began to emerge as well. The elven gods for the most part were happy to leave the other, younger races be, but lolth saw their rapid expansion across the globe, their harrowing of the planets resources, their plague-like nature, and urged the elven gods to teach the elves to stem this scourge upon the world. Specifically, she talked to her lover, Eruiaran, who initially agreed, and said he would speak to the others, for lolth bore little influence among the elven gods, but when he went to speak to them, he had changed his mind, betraying her trust in him and turning against her, saying that the elves were perfect as they were, and did not need to be burdened with the ravages of war, the lesser races would surely destroy themselves without the interference of the elves. This infuriated Lolth, and so she set about teaching her faithful followers in secret, using the cover of night and the moon to light their way
It wasn't long before the elven gods found out about this betrayal, and a great civil war broke out between Lolth's followers and the elves faithful to their pantheon. It was during this time that the elven gods cursed the drow with dark skin to show to the world the darkness within their hearts for all to see. Outnumbered, Lolth bade her followers to flee into the darkness of the depths of the earth, where they could gather their strength and one day purge the planet of their weaker cousins, and of the filth that pervaded the world, Lolth herself was cursed by Eruiaran with the form of a spider, so that none may ever be tricked by her again, that her visage remind all who interact with her of her treachery.
Forced to flee the heavens, Lolth settled in hell and created the demonweb pits, using the natural energies of hell to imbue the souls of her followers with ever more power. As time passed though, the life underground, and the afterlife in hell slowly warped the drow from a race seeking the redemption of nature to one of a hateful, spiteful race, wanting to see nothing but suffering and pain of those who had long ago scorned them, and the death of the mortal races who had caused this conflict to begin with.

A much less known myth, known only by the fey and those they tell the story to speaks of a much different tale.