Crocogar

A Crocogar is a "mighty reptilian beast" which lives (or probably, LIVED, after Nagash's little oopsie-poopsie) in the waterways of Nehekhara such as the Mortis River. The Crocogar Legion gained their name by slaying one.

Judging by the name and location, we're probably based off of Nile Crocodiles, but the "gar" in their name might imply they were a hybrid creature, half-crocodile and half-gar? Unless it was a reference to the species of crocodilian "gharial".