Rat Rider
From Warhammer - The Old World - Lexicanum
Rat Riders were a rare light cavalry unit deployed by the Skaven.
Overview
Mounted upon ferocious Giant Rats, Rat Riders were an infamous, if slightly hapless group of elite cavalry, mainly deployed within the experimental armies of Throt the Unclean. The Riders themselves were extremely confident in their abilities to evade enemy charges, if this failed they would simply flee and prepare to attack again. A unit of Rat Riders was commanded by an elite Rat Leader.