Devil Rats which have been exposed to a toxic background too long may sometimes mutate into plague rats. These rats have no body hair and virtually no pigment in their skin. Their veins are clearly visible underneath the skin. The extreme nature of their albinism reduces their vision so that they only see in the infrared range and grants them a severe allergy to sunlight. To compensate for the reduced vision they have excellent hearing.
Their natural immunity to toxins mutates turning their body into a veritable disease factory. Even the slightest scratch from these rats will expose the victim to the diseases they carry.
Due to being in constant pain, plague rats are excessively vicious. They will readily swarm and attack any creature no matter how large in size though they favor the injured. They have even been known to attack other plague rats if the target is sufficiently wounded.