Professor Veil Zebub is the alias employed by the demon Beelzebub during operations within human society. His human guise presents as a middle-aged to elderly man distinguished by a goatee, a pointy nose, and typically a red robe. His true demonic form manifests as a large fly-like monster, complete with four wings, three toes on each foot, and exoskeletal armor plates resembling shoulder pads.

In ancient Sodom, he held the position of a university professor. When God attacked the city, he rallied survivors to hear Satan's justification for the destruction. Witnessing Dante, Medusa, Zenon, and Satan resist God's hellfire and transform into demons solidified his allegiance to their cause.

Centuries later, he commanded a Satanist cult dedicated to resurrecting Dante. Using aliases like "Veil" and "Zebub," he infiltrated circles of Bible scholars and theologians. He masterminded the theft of the Holy Grail and Manora from the Duomo before journeying to Japan. There, he staged his own death during a terror attack; loyal cultists later retrieved his body and revived him for a Black Mass ritual. Saori Utsugi was designated the sacrifice, but her brother Ryo intervened with the God's Association, disrupting the ceremony.

Following this setback, he assembled fellow demons at an aquarium to confront a traitor among them. He disclosed prior awareness that the God's Association had been tipped off about the Black Mass but permitted it to proceed because Ryo Utsugi—a fellow demon—was Saori's brother, and their laws forbade sacrificing a member's kin.

The character's visual design incorporates inspiration from real-life Satanist Anton LaVey. The alias "Veil Zebub" originates from a specific translation choice in some adaptations, while his fly-like appearance remains consistent with the name Beelzebub.