End Rivalry

Pact (This spell can only be countered or removed from
play if exiled.)
End Rivalry enters the battlefield with X signature counters on it.
At the beginning of your end step, remove a signature counter from End Rivalry.
As long as there are signature counters on End Rivalry, prevent all combat damage that would be
dealt to all players and all creatures.
If there are no signature counters on End Rivalry,
exile it.