In the comics
Cyttorak existed as a deity (or demon) who received worship on Earth until under unknown circumstances he was banished from the Earth. He took up residence in a dimension known as the Crimson Cosmos, where time did not pass. Cyttorak has existed since the time of the ancient sorceress Morgan le Fay (during the time of the Seventh Century), and has even back then offered his magic to use as worshipers for power, as shown when Morgan used the Crimson Bands easily to bind Doctor Strange and Bolar.
Approximately one thousand years ago, a gathering of eight great magical beings took place. These beings -- Balthakk, Farallah, Ikonn, Krakkan, Raggadorr, Valtor, Watoomb, and Cyttorak - disagreed as to who had the greatest power. Hence, they settled on the Wager of the Octessence. Each being created an artifact with a fraction of their respective power, which would transform the first human who made physical contact with it into an Exemplar, a living personification of the power. Using outside agents, to construct temples to house the artifacts, the magical beings planned that the first mortal to find the artifact would trigger a spell that would quickly draw others to the remaining artifacts, creating eight Exemplars. Then would come the Ceremony of the Octessence, where a gathering of the Exemplars would attend the construction of a great magical engine, which would overwhelm the wills of all human beings. After the enslavement of humanity, each Examplar would rule an eighth of humanity, with subsequently a war between all Examplars in which only one would be left standing. Cyttorak managed to build a temple in a Southeast Asian country. He had a thrall demon named Xorak protect his temple for him.
At some point in the past, the great adept, the Ancient One, encountered and engaged in battle with Xorak near Cyttorak's temple.
Centuries ago a group of renegade monks tried to summon Cyttorak but instead brought his "most destructive aspect" to Southeast Asia. An adept named Gomurr, who served as the apprentice to "one of the most disreputable conjurers on the continent" opposed this avatar of Cyttorak. Gomurr received the aid of Tar, his friendly rival, as well as an "Initiate of the Ebon Vein." Gomurr and Tar, collaborating, succeeded in forcing this aspect of Cyttorak within the Crimson Gem of Cyttorak. Tar later attained the title of the "Protector of the Crimson Dawn", but Gomurr would later hold this office.
Cyttorak was last seen being released from a magical prison by Pete Wisdom during the Skrull invasion of Otherworld.
- Doctor Strange (Mentioned only)