Jason Blood is a world-famous occultist who actually originated from Arthurian times. Formerly one of King Arthur's knights, he was magically bonded with the demon Etrigan by Merlin for betraying Camelot.
Jason Blood was one of King Arthur's knights during the age of Camelot. He was seduced by the witch Morgaine Le Faye, who also promised him that they will rule Camelot together if he helped her. He betrayed his King and his people by opening the gates of Camelot to her invading armies, effectively sealing the kingdom's fall.
However, Blood was ultimately only a pawn in Morgaine's plot to allow her son, Mordred, to rule as King: she poisoned him with a viper's kiss.
As Blood lay writhing from Morgaine's poison kiss, Merlin appeared to the dying Knight. As punishment for his betrayal, Merlin bonded Blood with the demon Etrigan, "one of the vilest demons in Perdition". He was forced to hunt down Morgaine for all time, but he never succeeded, as she wore an amulet that enabled her to detect his presence.
Centuries later, Blood had become a recognized occultist, and used his bond with Etrigan to fight off beings of evil magic. Batman would seek out Blood's help in cases that involved the supernatural. At one point, Etrigan and Blood were separated by Klarion the Witch-Boy, and Batman had to reunite the two before Blood aged rapidly to death.
Etrigan assisted the Justice League in thwarting Morgaine Le Faye's attempt to capture the Philosopher's Stone to gain the power to rule the world. Etrigan appeared again to help the League when Mordred obtained the Amulet of First Magic.
When Morded turned against his mother using the Amulet of First Magic, Etrigan was somehow turned into a baby and set on Batman, Wonder Woman, Superman and Green Lantern by Mordred when they were regressed into children to stop him. Even as a baby, he still proved very formidable until Wonder Woman chastised him. He played a pivotal role against Mordred by chomping on the amulet, sending a massive wave across the continent and severely damaging the amulet, as well as stunning himself. In the end, the Leaguers were returned to normal, including Etrigan, who was still in Wonder Woman's arms, calling her "mommy" before the latter dropped him in disgust.
When Felix Faust took over Tartarus from Hades, the imbalance he set caused agony for the League's magic members, including Etrigan. Only when Wonder Woman and Hawkgirl stopped Faust was the balance of things restored.
Etrigan is a demon and therefore has superhuman strength and durability. He is also able to project fire from his body in the form of a blast, or a ball, or an explosion. He could also project freezing cold temperatures from his hands. He has also demonstrated the ability to cast powerful magic spells, as seen when he defeated and imprisoned Klarion in a magical duel. Even in the human form of Jason Blood, he is still highly-skilled in both armed and unarmed combat, as well as magic.
- "The Demon Within"
- "Chemistry" (Cameo)
- "A Knight of Shadows"
- "Initiation (Cameo)
- "Kid Stuff"
- "The Balance"