This weapon is nearly the same as the Light Crossbow of Speed, but since the mentioned crossbow is a +1 weapon, the drow variant weapon with +3 bonus to damage and -3 THAC0 with a speed factor of 1, is a lot better. But the +1 crossbow isn't made of adamantine and therefore can be used anywhere.
|“|| Drow Crossbow of Speed
A crossbow is a bow mounted crosswise on a wooden or metal shaft, the latter called a tiller. The bow is usually made of ash or yew. The crossbow fires a quarrel (also called a bolt). This item, like most drow equipment, is created using Adamantine, an alloy of adamantite that quickly turns to dust if removed from the Underdark.