He was one of Taboo's most trusted aides, on his debut, he effectively replaced General Deathgiller as Taboo's second-in-command. In the same time, he put Dr. Zazoriya and Dr. Iguana to death for numerous times of failures, marking the time that Deathdark becomes more serious and less humorous.
Deathmark usually stays in the Deathtopia, devising the plans to terrorize humanity for Taboo. After the death of Deathgiller, however, Deathmark took on the battlefield and shows that he's as much as a fighter as he is a tactician, wielding a demonic sword that sent the Goggle V into crushing defeat. However, he met his demise when the Goggle V changed their tactic by ramming the Goggle Golden Spear to him, slaying him in process.
- Deathmarks design is similar to Ambassador Hell from the original Kamen Rider Series in 1971.