The Game-Changing Host is a rare Legendary Creature — Human Wizard card from Unknown Event (UNK), collector number RZ05j.
Anything that could have changed The Game-Changing Host on the turn it enters applies retroactively. (He's been here the whole time.) {T}: Create a copy of a game changer at random. You may play the copy without paying its mana cost. (There are currently 61. Perhaps look at a list and randomize?)