Deimos was initially High Priest of the city-state of Thera, a realm in the land of Skartaris. Finally he obtained power to rule it.
He was a sinister figure who exuded power. He wished to rule all of Skartaris and fought the Warlord, Travis Morgan, multiple times.
He was finally killed by Morgan when Deimos kidnapped his love interest, Tara. However, Deimos was soon resurrected by his servants using the Mask of Life. Before his resurrection, Deimos' abilities were all derived from Atlantean technology. Afterwards, he gained true black magic abilities. Deimos would Kidnap Travis' son, Joshua, and clone him for the purpose of killing Morgan for him. Morgan would kill both the clone and Deimos. This cycle of death and resurrection would continue until Deimos struck a bargain with a being called the Evil One. The Evil One brought him back to life, but removed Deimos' black magic powers. Deimos and Travis would battle a final time until the Warlord decapitates him and throws his head to a wolf pack.
Deimos perished along with the other citizens of Skartaris during the events of Convergence.
Before his first resurrection Deimos had no powers and relied on Atlantean technology. When brought back by the Mask of Life he became immortal, could transform into a dragon or serpent, and gained the ability to summon demons. The Evil One would take away these abilities after he brought Deimos back to life.
In Other Media
Justice League Unlimited
Deimos appeared in an episode of Justice League Unlimited entitled "Chaos at the Earth's Core" voiced by Douglas Dunning. He is seen trying to conquer Skartaris. During his campaign, he was supplied futuristic weapons by Secret Society members Metallo and Silver Banshee in exchange for a huge Kryptonite rock. Deimos's army moved in on the citadel keeping the rocks, and fought Warlord's troops, who had recruited members of the Justice League. When Deimos managed to get inside the tabernacle, he was intercepted by Stargirl. He tried to fight her off with his special gauntlets, but her Staff overpowered him. Metallo promptly stepped in to handle Stargirl, until the Warlord engaged Deimos in a swordfight. During a battle, he met his apparent demise when he plummeted down a ledge.