Terror's full past and dimension of origin are uncertain. In the distant past, he battled a green bear-like demon that threatened early mankind, sacrificing his own form to overcome it; he was then cursed to wear its decayed form but gained its power. He began taking aliases describing the fear he inspired in others. In the Dark Ages of Earth-88194 (Shadowline), the still mostly human Shreck served as squire to the future Doctor Zero. Later, he fought as a black knight and found a woman to love him.
In the 20th century of Earth-88194 he served as enforcer for the Ravenscore crime family. He was sent to terminate the Knight of St. George, Michael Devlin, but was torn between separating train cars; he joined Doctor Zero to destroy the illusion-casting terrorist Marid before Devlin finally disposed of Shreck via piranha. Rebuilding himself, Shreck somehow traveled to Earth-616 (mainstream Earth) and established himself as the mercenary Terror, soon encountering the likes of Dr. Strange and Wolverine. Unable to kill target Roger Barbatos due to an immortality pact with Beelzeboul, Terror used the Hellfire Serpent to empower Mikal Drakonmegas as Hellfire and briefly trade him to Mikal's father Beelzeboul in exchange for cancelling the pact.
Terror's other adventures included teaming with Wolverine against eco-terrorists Monkey Wrench and Ecotage; encountering the Punisher while taking out Ray "Piranha" Jones; a conspiracy to create war in the Central American nation Medisuela; seeking the power of the Carnal Serpent and battling the god Priapus alongside Cage and Silver Sable; and joining Ghost Rider in banishing the demon Culex. Terror employs Ms. Alexis Primo, his personal assistant; Boneyard, to supply desired body parts; Brunnhilda, his tailor; and Rekrab, his occult expert.