The Crimson Gem of Cyttorak first appeared in Uncanny X-Men #13.

It has also been known as the Crimson Ruby of Cytorrak, the Ruby of the Crimson Bands and the Crimson Crystal of Cytorrak.

Origin

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.

The first Exemplar was Cain Marko, the one who activated the Crimson Gem's power when in the Temple of Cyttorak, just as the Temple was purposefully collapsed, an event that took him several years to free hismelf from as he was buried alive, only surviving thanks to his new power.

Juggernaut did indeed become the greatest Exemplar but only recently during World War Hulk was he given his true potential by Cyttorak.

Powers

Most commonly it bestows a complete (or at least greater) control over one's abilities but Cain Marko was bestowed the gift of becoming the Juggernaut after reading its inscription, "Whosoever touches this gem shall possess the power of the Crimson Bands of Cyttorak! Henceforth, you who read these words, shall become forevermore a human juggernaut!"

However at times in his early career when Cain worked alongside his best friend, Thomas Cassidy, the two shared the power of the Gem, which they believed would make them both unstoppable. Yet it did not work that way and instead made Juggernaut weaker, so the idea was eventually abandoned.