Markus Mortikus is a cruel, monstrous assassin-for-hire living in ancient Rome in the Gerosha Chronicles story The Tragedy of Lord Zeras, the first issue of the first volume, titled Origins and Fallout. His actions lead to the insane murderous rampages that lead to Zeras Carpathius becoming Lord Zeras, central to Gerosha multiverse mythology in Dozerfleet Comics.
Markus was born a few years after Zeras and Catalina. But unlike them, he never encountered the First Century Church as a child. He grew up to become a sadist, often kidnapping those that higher society officials didn't like and torturing them until the time came to murder them outright.
When Catalina and Zeras run away together, Markus is hired to hunt them down to the ends of the Earth and punish them. He manages to capture them at one point, and revels in whipping and sexually abusing them, all while celebrating the night away with prostitutes. However, he overestimates the security of Zeras' bondage. When he pries Zeras' eyes open to force Zeras to watch as Catalina is beheaded right in front of him, Zeras snaps and breaks free. Markus is killed in a fashion every bit as horrific as that he had in mind for Zeras to endure. The murderous rampage Zeras embarks on afterward leads to him becoming a fugitive from Rome, leading to Zeras fleeing toward a hill at exactly the right moment to get struck and bonded with the Marlquaan. From there, Meethlite civilization is born.
Markus had but one major creed regarding how he executed prisoners: Decolarent eam, eviscerate eum. This creed is then adopted by Zeras for how to execute only the most horrific violators of the law under Meethlite society. However, it eventually becomes a tool of terror; utilized by the Hebbleskin Gang when dealing with their political adversaries.
Markus was designated to be the most evil, cruel character that could possibly result in Zeras' rampages, and would explain Zeras' motivations for fleeing towards the Alps, ending up in the right place at the right time to become the first ever Marlquaanite. His name also made him into a sort of precursor to Melvin Markus, a cruel adversary of Miriam Flippo who rivals her abilities in hacking.
Markus' first official mention was going to be in the Classic Gerosha remake of The Battle for Gerosha, but that was abandoned when the Classic era continuity was. Instead, his first official mention was in the first draft of the Ciem: Vigilante Centipede first chapter "20,000 Legs into the Backstory;" which was written in October of 2010. Just like with Catalina, plans were in 2010 to have a story separate from Vigilante Centipede that would eventually expand on his role in Gerosha mythos. That story premise became The Tragedy of Lord Zeras. In addition to becoming an excuse for Zeras' fugitive status, Markus became an excuse for why Duke Arfaas is so obsessed with collecting the Flippo Triplets' heads as trophies.