The volcra are one of the many creatures living in the Shadow Fold that feast on human flesh.
Volcra have long, dirty claws, leathery wings, and rows of razor-sharp teeth. They are blind from living in the Fold for so long, but are said to be able to smell human blood from miles away.
Baghra reveals to Alina Starkov that the volcra were a mistake. The volcra used to be human long ago, but the Fold changed them into monsters. Baghra calls them "his punishment, a living testimony to his arrogance." -p 238