Varrangoin

Varrangoin, or abyssal bats, are native to the Abyss but found in both that plane and Carceri. They're like giant bats with rotted wings and skeletal bodies. They have long, forked tails, and their heads are skull-like with glowing red eyes and sharp fangs. They undergo ritual scarification when young, and varrangoin spellcasters use these scars as spellbooks.

The 337th layer of the Abyss, the Plains of Gallenshu, is dotted with the ruins of ancient varrangoin cities, long since destroyed by armanites and other Tanar'ri. The varrangoin hate the tanar'ri for taking over their realm, and hope to destroy them. Their war leader is Vis Nirrin Vis.