... one of the players (except the observer player) has left
or
a hero has been killed (Knockout; the owner of the killing hero wins)
or
the time is up and both heroes have the same remaining HP (Draw)
or
the time is up and a hero's HP remaining is less than of that of his/her opponent (Win on Points; the player who owns the latter wins).
ENJOY PLAYING THE HERO RUMBLE LEAGUE!