Verminator-X, also known as Manx is a feline mutant and, one time friend though now, enemy of the Turtles.
In the primary continuity Manx was an apprentice of Donatello who went rouge because of his abuse of cybernetic implants in a vain quest for immortality. Driven mad he adopted the villainous persona of Verminator-X. Verminator-X then attempted to destroy the Turtles by forming an alliance with Shredder and Armaggon.
TMNT/Gargoyles Crossover Continuity by CelgressEdit
In this fanfiction continuity Manx is a mutated Foster Fenwick the nephew of Vernon Fenwick aka Armaggon. Armaggon along with his henchmutants, Scale Tail & Killer Bee, abducted the sixteen year old genius university student Foster and philanthropist heiress Janine Renard from the Manhattan Animal Behavioral Research Institute, when Armaggon was unable to successfully replicate the formula for mutagen on his own. Using what little mutagen he still possessed Armaggon transformed Foster into the humanoid cougar Manx while changing Janine Renard into the humanoid artic fox Alopex. Having little choice left in a world where nonhumans are increasingly hated and feared, Manx & Alopex joined Armaggon's gang of criminal mutants. Though the pair plan on betraying their nominal leader, and tormentor, when the time is right.