The Fallen One was originally a Herald of the cosmic entity Galactus, and was his first attempt at creating a servant. Unlike later Heralds, the Fallen One was empowered by dark energy as opposed to cosmic radiation. The Fallen One, however, proved to be very cruel and was eventually imprisoned by Galactus. The Fallen One managed to escape and repeatedly attacked Galactus, who always defeated his former Herald. The hero Star-Lord eventually imprisoned the Fallen One in the inter-galactic prison the Kyln. The Fallen One escaped when the Kyln was destroyed in a conflict between Thanos and the entity the Maker. Although the Fallen One found Galactus once again, Galactus simply teleported him back to Thanos to deal with. Thanos managed to defeat the Fallen One by tricking him into igniting a gas giant, which rendered him unconscious. Thanos then mentally enslaved him, forcing him to serve as Thanos' Herald.
The Fallen One later battled the Proemial Gods Tenebrous and Aegis, who killed him and presented his remains to Thanos in a gesture of contempt.
The Fallen One, unlike later Heralds, was granted control of black matter, the "binding halo by which galaxies are made solvent". The Fallen One could use this matter to augment strength, reflexes and durability, project energy, control the electromagnetic spectrum, manipulate matter and allow total immunity to the rigors of space. The Fallen One was also capable of traveling faster than the speed of light.