Very little is known about Deathurge's origins. He acts as Oblivion's herald in action if not in title. In some cases he acts very much as an Angel of Death, guiding souls into whatever afterlife awaits them, seeming almost benevolent at times. In others he furthers the goals of Oblivion across the universe, snuffing the lifeforce of any who oppose them.
Mayor Story Arcs
He is first encountered under the employ of the villain Maelstrom as he is dispatched to slay the cloned bodies of his minions, later slaying the clone of Maelstrom himself after his defeat by the Avengers. Later it was revealed that Deathurge never really served Maelstrom at all, he merely was made to assist Maelstrom at Oblivion's behest because Oblivion foresaw Maelstrom's potential to upset the balance in Oblivion's favor.
Later, Deathurge encountered Quasar on the surface of Uranus. Noting Quasar's dissatisfaction with his life, Deathurge attempted to assist Quasar in ending it, most likely because Oblivion also foresees Quasar's potential to upset the balance in life's favor. Just as it seemed Deathurge was victorious, Eon intervened and appointed Quasar Protector of the Universe. Deathurge was quickly defeated by Quasar who was empowered by the Life-Urge, however, Deathurge prophetically tells Quasar: "One day you will beg me to kill you… and I will refuse".
Deathurge clashes with Quasar multiple times over the next several years. As Quasar was slowing dying from wounds inflicted upon him by Maelstrom, he indeed begged Deathurge to kill him, and indeed Deathurge refused. Finally, after Quasar had died, Ghost Rider arrived to enact vengeance and was met by Deathurge, the two fought to a stalemate.
Later, when Maelstrom had stopped the Earth's rotation, he ordered Deathurge to blind the Watcher but he vanished before Deathurge's weapons could find their mark. Deathurge was also sent to kill Doctor Strange who was assisting most of the world's mystics in staving off the detrimental effects. However, Deathurge was intercepted by the Squadron Supreme. Later, Quasar, resolved to use the Ultimate Nullifier (which in and of itself is suicidal) against the Magus, received a visit from Deathurge. The two fought to a standstill, neither one having any real advantage over the other.
Deathurge also compelled Patsy Walker to commit suicide.
Great Lake Avengers
Most recently, it was revealed that Deathurge was Mr. Immortal's imaginary friend growing up. He involved himself in Hollis' life, often taking family members and close friends from him. Later, when Hollis became Mr. Immortal and founded the Great Lakes Avengers, Deathurge continued to talk to him. Hollis finally snapped when Maelstrom killed Dinah Soar and Deathurge took her to the afterlife. He blamed Deathurge for taking his friends, but never taking him. Deathurge finally felt regret over the situation and assisted the GLA foiling Maelstrom's plans. He was replaced as Oblivion's agent by Doorman because he betrayed Maelstrom and failed to bring the soul of Squirrel Girl’s sidekick, Monkey Joe to the realm of Oblivion. Now trapped in the form of a squirrel, Deathurge was last seen attempting to kill Squirrel girl's new sidekick, Tippy Toe, but falling in love with her instead.
As an immaterial cosmic force, Deathurge can appear material or intangible. He can survive extreme temperatures and the rigors of space. His body is composed of an unknown material or energy, which he claims is the "midnight in all mortal souls," and he can pull weapons from his body composed of the same material. He can also form skis of this material in order to travel at interstellar speed. As an agent of death, Deathurge can sense the imminent death of another, will guide his or her spirit to the afterlife, and appears in a recognizable form similar to the deceased's own species.
Deathurge can become intangible at will, and draw forth from his non-reflective ebony body a variety of simple weaponry such as swords, spears, axes, bows, and arrows. These weapons, also non-reflective black, appear to be made of the same unknown substance as Deathurge's body. These weapons do not inflict physical wounds, but are imbued with life-annihilating properties that can kill even powerful superhuman entities. He can also fly at great speeds but only on ebony skis created from his body.
In general, a person's will to live plays a large part in how effective his weapons are. When Deathurge attacks, he is typically seeking to slay a specific target - usually someone who at least to some degree craves death and oblivion. If one of his weapons scores a direct hit on his target, the result is fatal, with a blackness spreading from the spot where the weapon bloodlessly struck and passed through the target's body.
If the weapon only strikes a glancing blow, or it happens to pass through someone other than Deathurge's target, then that person will feel the sensation of numbing coldness but will not blacken or die. If a target does not wish to die, or can at the brink of death find a strong will to live, Deathurge's powers have a diminished or even negligible effect.