Wellbuth was a minor demon from the original Devilman manga.
Wellbuth was a giant demon that was a mass fusion of many other Demons, having features resembling birds, insects and fish across his body, his chest resembling a mass lump of flesh.
Wellbuth could fly through his wings and attack with his claws. Not to mention chew and tear with his mighty jaws.
Wellbuth took part in the massacre of the Angels who descended the Earth in the Cretaceous era. He is either killed in the attack or is sent into hibernation like many other of his brethren.