In the 1930's scientist Ian Karkull and his partner Everett Dahlen found the lost city of Ragnor located in the Sahara. They quarrelled over a ruby that they had discovered. Everett struck Karkull unconscious, took the ruby, and left him to die in the fabled city.
Karkull awoke and was found wandering the desert by nomads. He vowed to seek vengeance against Everett and the entire world.
Karkull invented a device that could turn person into an intangible living black shadow and then restore him back to his human form, even over considerable distancs. Karkull hired a petty criminal, named Hart, and turned him into a living shadow to kill Dahlen. Karkull then formed a partnership with Hart's boss.
The first Doctor Fate investigated Dahlen's death. He confronted Karkull, who had transformed himself into a shadow. Dr. Fate's magic was useless against Karkull's shadow. Fate destroyed the machine and left Karkull in shadow form.
Karkull formed an alliance with Wotan, Dr. Fate's enemy. They created advance weaponry to destroy the world at a domed city in the Arctic. The domed city went up in flames during the clash wit Dr. Fate. All three escaped the encounter.
Karkull was able to see into the future. June 28, 1941 he and other villians he had recruited were to kill President Franklin D. Roosevelt and the eight other men who would be his successors. Dr. Fate and the other members of the JSA thwarted him. Wotan killed one boy who may have been President Ronald Reagan's successor.
Dr. Fate clashed with Karkull, but it was the Spectre who caused his shadow form to explode. This explosion irradiated the people around Karkull and bathed them temporal energy that had stolen other people's future lives.
The result was a retardation of aging and added vitality while they lived. Those affected were the original Atom, the first Doctor Fate, Jay Garrick and his future wife Joan Williams, Alan Scott, Hawkgirl and the first Hawkman, the first Hourman, the 40's Johnny Thunder, Wesley Dodds, and the first Starman.
He was seemingly destroyed in this encounter. He was later to have been transported to the shadowlands where he became stronger and a more powerful living shadow. He has fought the new JSA when they reformed. He and Mordru teamed up against Obsidian before he lost and was sent back to the shadowlands.
Karkull has access to the Shadowlands, which allows him to manipulate darkness. This allows him to become intangible, and he has some form of energy absorption as well. Because he has access to the Shadowlands, he is able to draw shadows trapped in Ragnor and use them to his advantage.
Karkull is also very smart, being an accomplished scientist. He was capable of creating a machine which turns humans into shadows. He used it on himself, and when it was destroyed by Doctor Fate, he was stuck in his shadow form.