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, they'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 like some sort of hybrid critter from "Avatar: The Last Airbender"? Unless it was a reference to the species of crocodilian "gharial".