Bystoma

A hideous, amphibian-type Zoanoid; covered in slimy skin and possessed of several fin-like structures on its limbs and on its hunched back; it also has a powerful tail ending in a powerful, fan-like fin.

The fins - which can be folded back - like a lion-fish' fins, end in sharp spikes, which are extremely venomous; humans die within moments after contact.