While this was inspired by one of numerous demons defeated by Conan the Cimmerian, creature's description was so short and imprecise that It's almost completely my invention. Therefore it is not only published as Conan illustration but as a generic demon/monster. Perhaps it could be a flying kaiju as well?
Anyway the quote simply states it had bat-like wings.
"...Its wings were bat-like; but its body and the dim face that gazed down upon her were like nothing of sea or earth or air; she knew she looked upon ultimate horror, upon black, cosmic foulness born in the night-black gulfs beyond the reach of a mad-man’s wildest dreams.
“A devil from the Outer Dark,” he grunted. “Oh, they’re nothing uncommon. They lurk as thick as fleas outside the belt of light which surrounds this world." "
Robert. E Howard, The Vale of Lost Women