Mutates have a collective mind, their individual cells almost act and think differently from the host creature. After awhile, the host creature is lost amongst the many creatures it has merged with. Mutates in general have a great ability to heal themselves even of the most severe wounds. That is why this Fiend was able to quickly reattach its arm to its body so quickly.

The mutate infection will infect a single creature and that creature, an imp, will build onto itself. If they live through the survival of the fittest, they can live tens, if not hundreds of thousands of years and grow to be enormous creatures. Only Ancients have lived longer than the oldest mutates.