In all of the history, one constant has always been showed. There will be always fighters. They will fight for freedom, for power, for pride, to protect, for fun, or for any more reasons. Have you ever thought about what would happen if you got the best fighters from all time and put them in one tournament? That's what the trickster deity that calls themself "The Host" thought about.
He put on what they thought was the best of the best to battle and see who is the Temporal Champion.