Cap first appeared in the original Decap story as a beast from the Underworld who wished to have an army of the undead based on Chuck D. Head, Frank's latest creation. Max's castle rose from underneath the Earth to reside right next to Castle Frank N. Stein, where the demon leant over his wall and announced his plans (as written by Rupert, although the effect was somewhat lost in the delivery). In case Frank decided to resist, Max launched an invasion of his castle with his Hellish minions, including Bullhead and Croc, and removed Chuck from the equation by having him thrown off the castle. After this, Max D. Cap inhabited Castle Frank N. Stein and continuously pestered his new host to finish his army (having Loyd Grossman out of the building in the process). When it became apparent that Chuck's creation was only a fluke, Max sent Bullhead and Croc to capture Chuck, but only succeeded in watching him die for the second time. Exasperated, Max went searching on his own and quickly came across Chuck, engaging in a fight (egged on by Rupert). With his flame breath and superior strength, Cap was easily winning the fight but was interrupted when Frank revealed he had finished the first of his new army - a Blockbusters contestant! Disgusted by Stein's idea of an undead creation, Max D. Cap fled back to his castle, pausing long enough for a final threat (as suggested by Rupert). With that, the castle sank back underground.
Max D. Cap later appeared in an unlikely place, manning the death train to Hell. His reacquaintance with Frank was cordial enough until Rupert tried to convince Max that the heroes were all dead (their names had actually been added to the 'dead' list with a pen). Ready to let them all go, Max faced a dilemma with keeping them in Hell since they were not actually dead and objected to Rupert pulling out a gun to rectify the situation. The monster tried to calm everyone down, but a headbutt from Chuck pushed the berserk button and caused max to unleash his fiery breath on everyone (including all the corpses on the train, much to his regret). Once the train had stopped, Max was berated by the Thin Controller for accidentally bringing alive down again but let him off. Chuck D. Head attempted to escape and Max was among many bowled over by the thrown Head. After the Thin Controller decided to keep Frank for herself, she ordered Max to let the other three go free.
- Max appears in the original Decap Attack video game but is much more of a stereotypical devil than his cowardly, apologetic appearance in the comic.