All Maw have infernal blood and have the same infernal traits such as horns, forked tongues, tails and talons.
Due to the War on Lavant and the Diablo War in Westcrown, Maw are feared by the general populace and for many the stuff of nightmares.
Originally created by The Mother of Monsters to destroy the Lavant Kings many Maw have been corrupted by The Dark One (and that's the majority).
Although the Maw are Darkly Aspected not all are truly evil some have become Neutral with a few exceptions being turned to the light...
D&D 5E: see Tiefling