Battle Royal

At the beginning of each end step put a Level
counter on Battle Royal, then if it has 5 or more Level counters remove all Level counters on it, give it a Limit counter, and choose two random creatures control by different players, those creatures fight. Repeat, choosing different players until each player has been selected at most once. Exile all creatures destroyed by this fighting.
At the beginning of each upkeep, if Battle Royal has 4 Limit counters on it Exile it and return all creatures Exiled by i