In the 6th Century, Modred was an apprentice magician under Gervasse and betrothed to Gervasse's daughter Janice. Modred was asked to become an apprentice by "Merlin." However, after hearing tales of madness, he declined. Thinking the power of the Darkhold could oppose the mad wizard, he went to the tower to claim it. He battled the Other (Chthon) until Janice came in. Rather than have her become corrupted, Modred gave himself up. Gervasse sealed Modred in a crypt hoping that future generations might be able to help him.
Modred was resurrected in modern times by Janet Lyton and Grant Whittaker. He was startled by the changes to the world but managed to protect the couple when the Other came to claim him.
Since then, he has fallen under and out of Chthon's control and encountered many heroes and villains. When Chthon's possession takes over, Modred is a very dangerous individual. One can never tell when he will change, as the Scarlet Witch found out as he helped her reach Wundagore to learn about her past, then attempted to offer her to Chthon.
When Modred is in control of himself, he will help others fight evil, although his actions usually have his own interests at heart. For example, he helped Puck against the Brass Bishop thinking that he could find a method to retrieve his soul and end his possession. He also briefly assisted Spider-Woman (Jessica Drew).
He also attacked Captain Britain due to his association with Merlin. He seemed unaware that Brian served the true Merlyn and not the impostor Merlin he knew in the past.
After the initially formed Darkhold Redeemers fought and successfully defeated Donald J Walsh, a record producer turned into a mass of worms in human form, Modred appeared and crushed the last worm, vowing to keep an eye on the Redeemers. He later saved the Redeemers from Darkhold cult hitmen, and later informed them that they needed to go to the town of Perfection. When the N'Garai came to Perfection, Modred brought the Darkhold Redeemers and was able to coerce Sabretooth to help. While Creed and the other Darkhold Redeemers battled the creatures, Modred examined the cairn. Thinking that Chthon might be on the other side, he saved a woman, then tossed her through the portal. The resulting screams convinced Modred that he should not try to use it. He then whisked Sabretooth away before he could kill Sam Buchanan (whom he shared a past with) or anyone else. The other Redeemers realized that Modred had simply used them for his own goals rather than trying to save the townspeople. The Redeemers found themselves on Maui and encountered Dr. Strange, the Scarlet Witch, and Agatha Harkness. Modred and Dr. Strange fought, with Modred swearing to not leave the soil (of Maui) until he was "driven hence in defeat." He swore this as he was bleeding, creating a geas that bound him to Maui. Attempts to lose a drinking contest proved futile, and Modred could only rage as he sensed another page would be used soon (the Page of the Demogorge). He would later circumvent this geas by carrying a small bag with soil from Maui inside.
Blade, obsessed with finally destroying all supernatural beings, read a page of the Darkhold that turned him into the Demogorge, who would absorb the abilities and knowledge of any supernatural beings he killed. Now called Switchblade, he hunted his former allies. He was opposed by Modred, who eventually fell to Switchblade, but not before emptying his bag of Maui soil, ensuring pain for Switchblade whenever Modred's powers were used. Modred and the others killed by Switchblade were resurrected when Louise Hastings read the counterspell from the Darkhold.
Returned to life, Modred was approached by the Darkhold Dwarf. He was offered his soul back if he would trade his powers with an innocent holy woman. He did this, tricking the blind holy woman, who regresses in age upon possession and is revealed to be Janice, Mordred's love. After a brief battle, Modred takes back the power (resulting in Janice's death) which taunts him. Modred became Jinx's instructor in the mystic arts. During the Siege of Darkness Jinx and Modred fought, as Morbius convinced Jinx that Modred had killed his grandmother, Louise. Later, the Darkhold Redeemers were sent to find the Blood known as Truthsayer. Under assault from the Fallen called Metarchus, Modred held his own. Metarchus took Modred's form and seemingly slew Truthsayer. Later, at Louise Hastings' funeral, Modred teleported Jinx to live with Vitorrio Montesi. After everyone else left, it was revealed that Modred killed Truthsayer, as she was about to reveal Victoria Montesi's true origins.
Modred began tutoring Kyllian Boddicker (Earth-616) (who was now calling himself Wildpride) in the mystic arts. Teaming with Jack Russell, Morbius, and Vengeance, they confronted Salome, to who Mordred offered a deal to power over the Midnight Sons in exchange for slaying Doctor Strange. Salome rejected his offer and struck him savagely.
Wildpride confronted Doctor Strange (at Modred's behest) on the grounds of the latter's former sanctum. Modred arrived and revealed he was searching for Victoria Montesi, pregnant with his master, Cthon. Modred was aware she was hidden in Strange's new sanctum, and attempted to enter it, gaining entry to the Tempo building disguised as a plumber. Doctor Strange easily ejected Modred, temporarily removed his powers, and left him in Thailand.
