The Crimson Gem of Cyttorak first appeared in Uncanny X-Men #12.
It has also been known as the Crimson Ruby of Cytorrak, the Ruby of the Crimson Bands and the Crimson Crystal of Cytorrak.
The Crimson Gem of Cyttorak was created because of a wager that took place one thousand years ago by the Octessence, eight mighty beings. They each put their power into an item and decided that the first mortal to come into physical contact with each being's respective item would become an Exemplar, possessing the power of the being who created the item they interacted with.
See also: Juggernaut and Cyttorak.
However Cyttorak cheated and had many Avatars without starting the wager. It wasn't until another Exemplar was created that the wager began. His avatar at the time was Cain Marko.
Most commonly it bestows a mortal with the powers of The Juggernaut. Being a powerful mystical artifact it has been used for teleportation and creating mystical constructs and energy blast.