Volthoom is the main antagonist of Wrath of the First Lantern story of the Green Lanterns.
Volthoom was an ancient being with the ability to warp reality. He was taken before the Guardians of the Universe, who offered him a position as their agent, known as the First Lantern. However, Volthoom eventually grew prideful and was imprisoned in an unbreakable chamber and wrote out of their history.
After the War of Lights, the Guardians, as part of a plan to replace the Green Lantern Corps, moved Volthoom into lesser constraints. Using Volthoom's DNA, the Guardians created trhe Third Army, a horde fo infectious warriors that nearly assimilated all sentient life in the galaxy before being stopped by the Green Lanterns.
The Guardians later inadvertently freed Volthoom, who captured them and attempted to siphon energy from the Green Lanterns in an attempt to gain enough power to rewrite the universe. However, he was ultimated defeated by the Lantern Corps. He was weakend by Nekron and separated from his connection to the Emotional Spectrum by Hal Jordan. Utterly powerless, Volthoom was killed by Nekron.