The Drow and the Underdark

The Drow are dark mirrors of the Elves. Banished long ago by the Elves and Dwarfs, they fled to a benighted other dimension, a place of continuos darkness. Only by delving the deepest tunnels can one find their other worldly realm.
The Drow live in a Matriarchal society which values deceit cunning and strength. Each Drow hails from one of the great Houses, the clans which fled Millenia ago. These houses constantly vie for power and the attention of Lloth, Demon Queen of Spiders.
Drow wear ensorcelled armor, bound with the nature of their dark realm. Their weapons are made of strange metals and leathers, spider silk robes and resin shields. They like to cause pain to others, sometimes leaving those to suffer rather than vanquishing them. Drow dislike mercy, and see it as a weakness, but are well known slavers, so the rarely kill everyone in a raid.
It is unknown how the Drow travel so quickly from their Realm to the lands of men. But they rarely leave anyone to speak of their raids in the first place. They are shadows in the night, always gone before the dawn.