Scour

Scour was a Voidharrow demon who entered Toril through a gate from another universe with his "sibling" Murmur hundreds of years before the Spellplague. Scour's consciousness was scattered into many pieces but Murmur was apparently able to revive much of Scour's mind.

By 1480 DR, Scour was in Luskan, manifesting as a swarm of mutated vermin. Scour infected many inhabitants with the Fury plague, which caused victims to go into a homicidal rage. Scour attacked an assembly of Luskan's gangs, killing many people. He was confronted in Luskan's underground by Kalen Dren, Myrin Darkdance, and Sithe and defeated. Sithe sacrificed herself by using her innate abilities to open a portal to the void where she took the remaining fragments of Scour.

Appearance
Scour's corporal form, such as it was, consisted of a mass of mutated vermin.