Ikthalon is an extra-dimensional demon of unknown origin. Daimon Hellstrom commented that he had been active on Earth around medieval times, but his past history has not been detailed.
A faculty member at Gateway University, displeased with the changes occurring in the process of modernization, made a pact with Ikthalon to resist those changes. Ikthalon first made his presence felt in the Communications Building (from which the pact had been made), causing levitation of inanimate matter, and other poltergeist-like phenomena. These progressed over several weeks, and then Ikthalon and his legions caused the entire, newly-installed heating system to freeze solid. A janitor then saw one of the Legions of Boreas stalking the building at night. Next Ikthalon caused the building to be engulfed in icy blue flames, which did not burn.
Dr. Katherine Reynolds contacted the exorcist Daimon Hellstrom to investigate the possession of the Communications Building at Gateway. Hellstrom agreed and investigated the building as the Son of Satan. He placed a mystic ankh on the doorstep of the building to prevent any demons from leaving the building. As he explored the building, he was ambushed by one of Ikthalon's Legions, who grabbed him and pulled him into a portal which brought him to Boreas. Hellstrom's trident was knocked from his grasp as he was attacked, and without it he was overpowered and imprisoned by Ikthalon. Ikthalon and his Legions then opened a portal to Earth, but found they were unable to escape the building due to the presence of the ankh.
However, Katherine Reynolds, along with the building's janitor, defied Hellstrom's instructions and decided to see what was going on in the building as well. The janitor mistook the ankh for some type of graffiti, and erased it. This allowed Ikthalon and his Legions freedom to travel outside the building, and they emerged and attacked Dr. Reynolds and the janitor. Seeking some means to defend herself against the demons, Dr. Reynolds picked up Hellstrom's trident. Her contact made a connection to Hellstrom, who was able to use it to return to Earth and attack the demons. Ikthalon took Reynolds hostage and forced Hellstrom to give an oath not to fight him. However, as soon as Ikthalon released Reynolds, Hellstrom, destroyed Ikthalon with a burst of hellfire, claiming it was his right to lie as the son of the great deceiver.
Ikthalon has been invoked in spells since that time, indicating he still existed in some form. During a dream sequence under the control of Dream Weaver, Clea was bound by "the Icy Tendrils of Ikthalon."
Ian McNee invoked Ikthalon in a fight against an unnamed sorcerer by using the Wrath of the Chill Ikthalon.