Gargoyles S02E02 - Metamorphosis

Geneticist Doctor Sevarius was hired by Xanatos to create replicas of the Gargoyles, but the mutations he's created are a cross between jungle cats, bats and electric eels. Derek shields Xanatos from an attack and is infected by the Mutate serum, but the Gargoyles raid the facility before Sevarius is complete and he is killed indirectly as a result. However, it is later revealed to have been a ruse to hide Sevarious. Sevarious continues to work for Xanatos in secret.