Colfenor's Urn

Whenever a creature with toughness 4 or greater is put into your graveyard from the battlefield, you may exile it.
At the beginning of the end step, if three or more cards have been exiled with this artifact, sacrifice it. If you do, return those cards to the battlefield under their owner's control.

Whenever a creature with toughness 4 or greater is put into your graveyard from play, you may remove it from the game.
At end of turn, if three or more cards have been removed from the game with Colfenor's Urn, sacrifice it. If you do, return those cards to play under their owner's control.