Majeston Zelia has a great number of abilities. She can shoot energy blasts from her hands, fly and siphon energy from other gods (notably Odin). She supposedly has "infinite vision", allowing her to see persons and events far removed from her physical body. She can summon the Dark Gods to temporarily merge in a single body.
The origin of the Dark Gods and Zelia is unknown. They built a city called Narcisson, an evil twin of Asgard, and ruled from there. When Odin send Asgardian scouts to explore the universe, one of them entered the realm of the Dark Gods. Lonkarr, the scout, was recognized as an invader and attacked by a goddess, Tserron. They fought for hours in a combat ending with Tserron's death. Since the dead goddess was Perrikus' wife and Zelia's daughter-in-law, the two races of gods soon entered war.
The dark Gods emerged victorious but Zelia hesitated to finish them. She offered Odin a position as her consort in exchange for the continued survival of the Asgardians. He refused and stood facing execution. A very young Thor chose the moment to threw his father a spear and allowed Odin to counterattack. Rallying the Asgardians to a renewed charge, this time Odin won. He banished the Dark Gods back to their realm. He only kept Perrikus as a prisoner. Odin chose to erase the memories of the war and its atrocities from the minds of the other Asgardians.
Centuries later, Zelia took advantage of a low point for the Asgardians to attack them again. She attacked and managed to capture most of its population. Asgard was left abandoned. She toyed with the captive Odin while turning her attention against the Olympians. She was later defeated by a combined attack by Thor, Hercules, the Destroyer and a freed Odin. The Dark Gods were left scattered across the universe but are probably still active.