Giant Rat

From HammerWiki

In the great labs of Clan Moulder, one of the easiest creatures to create and cheapest for other clans to buy are the great Giant Rats, making them a very common sight on Skaven battlefields. They are rats that have been mutated with Warpstone until they have grown to the size of wolves. Also, in order to maintain order among these rats, a Packmaster is usually present with a whip to urge them forward. Without this Packmaster, the Skaven army will have a very hard time controlling the mutant creatures.