Necromundan Giant Rats
As is to be expected of an environment where the deadliest and most exotic of vermin abound, Necromunda's Underhive is not infested with regular rats. The mutant strains that have developed here over the centuries vary greatly, though Giant Rats can reach up to four feet in length (not including the tail), while some of the even larger specimens can have razor sharp teeth as long as one foot.
Over the generations, these mutated rodents have also begun to display a low form of animal cunning. This, coupled with incredibly fast natural reactions, means that they have an uncanny ability to avoid almost any shot aimed at them.