Sewage Banshee Grendel
The Sewage Banshee Grendels are one of two Toxic Grendel breeds by Grendel Man. They are like Toxic Norns in the fact they can live in a toxic environment. But they cannot take any cures at all, only toxins. Medicine One, in particular, can quickly kill a sewage banshee. Also, they are amphibious, and were intended to not be able to lay eggs out of water (although this is not implemented in practice).