Gregor Markov is the son of King Viktor of Markovia. His brother is Brion Markov, who would become the super-hero Geo-Force, and his illegitimate sister is Tara Markov, who would become the super-hero Terra.
Prince Gregor's father King Viktor died during a revolution staged by Baron Bedlam. Gregor became King. His brother Prince Brion used scientist Helga Jace to develop super-powers, making him into the super-hero Geo-Force. Gregor went into battle against Bedlam's army hopelessly outnumbered, manning a tank. Markovia was saved by the intervention of Batman and the Outsiders. Geo-Force threw Bedlam to the people, who executed him. Gregor was sad to see Brion leave for Gotham City with the others. He told the people that his first act was sending Prince Brion to learn and study in America.
Bedlam returns from the dead to stage another coup, and kidnaps Gregor's fiancee Princess Ilona. Reporter Joan Lincoln tries to help King Gregor get his story out, but no news networks are interested. Bedlam attacks Castle Markov with the Masters of Disaster and captures King Gregor. Gregor, Ilona, and Lincoln are all sentenced to death by firing squad. The Outsiders rally the Markovian army to attack Bedlam, and Geo-Force rescues his brother at the last moment. For crimes against Markovia, Geo-Force decapitates Baron Bedlam. King Gregor gives the Markovian Medal of Honor to all of the Outsiders. He asks them to become Markovia's unofficial "agents of change," dealing with threats that world government is forced to ignore. King Gregor has a beautiful wedding ceremony to Princess Ilona. The Outsiders accept his proposal.
The Outsiders approach King Gregor again when they're tracking Bad Samaritan. Gregor provides them with fake identification to help them go undercover in the Soviet Union. When the Outsiders are kidnapped by President Bentama, Gregor is angry that he cannot intervene for political reasons. Gregor is threatened when the Masters of Disaster escape Markovian prison, but they decide he is worth more as a messenger to Geo-Force. Lincoln interviews Gregor again when his country is electing a new prime minister.
Psycho-Pirate poses as Baron Bedlam to stage another coup in Markovia. Gregor and Ilona are imprisoned in the dungeon. They are rescued by the Outsiders working together with Infinity, Inc.. Gregor calls the Outsiders back to Markovia when the secret of their connection is revealed to the world. The U.S. government threatens to withdraw all support from Markovia unless they give up the names of the Outsiders. Brion and Gregor have a huge argument. Helga Jace uses poison gas to assassinate King Gregor while he is meeting with U.S. government officials. Brion becomes the next King of Markovia. During the coronation ceremony, Jace brainwashes Ilona to accuse Brion of murdering Gregor. Ilona also reveals that she is carrying Gregor's true heir.