Infinite Tournament
The Infinite Tournament is an event hosted by an enigmatic God machine known as Mazabon who projects himself as a tall humanoid with a cane and a tall hat. Mazabon goes by many different names and appearances, but regardless, he hosts a tournament that takes place across the multiverse pitting individuals and whole civilizations against one another in a spectacle.
Contestants are often unwilling participants abducted from their home universe. They are pitted in a fight to the death, but neither party actually dies. A pocket universe is created for a specific tournament, and it can be reset as needed. That is, even if a contestant dies, they can be brought back to life as Mazabon can merely turn back time.
Origins
Mazabon started off as a member of the board of directors in the Omniverse Nexus. When he discovered the threat of the Basilisk, he began to run simulations on how to defeat it once and for all. He traveled across the history of multiple universes, studying the evolution of various species and civilizations in search of one that might be powerful enough to wipe the Basilisk from reality. As such, he held a contest of champions where in these simulations, species and civilizations would battle it out for the chance to become powerful enough to take on the monumental task of defeating the Basilisk. It was during these tournaments that Mazabon began to theorize the Basilisk Equation - the mathematical formula that could prove definitely that the Basilisk could be destroyed.
However, Mazabon's search became nigh infinitesimally endless as his computational sanity degraded from his time creating simulations. Eventually, he forgot the true purpose of making the Infinite Tournament and began holding tournaments for sadistic entertainment. Other versions of Mazabon did much the same. As the Omniverse Nexus perceived the possibility that Mazabon could evolve into a threat on par with the Basilisk, he was banished from the Omniverse Nexus, and safeguards were put in place to ensure he could not meddle with Omni 01.
Nonetheless, Mazabon found loopholes to interacting with Omni 01 civilizations by creating micro-timeline splits that would abduct individuals, then erase their memories of ever visiting the Infinite Tournament. Other targets include the recently deceased, grabbing an individual's consciousness while leaving their dead body behind.