Grim's Death Contract

Grim's Death Contract enters the battlefield with
X counters on it.
During each player's end step, that player return
a creature to the battlefield from their graveyard
with X or less converted mana cost where X is
equal to the number of counters on Grim's
Death Contract. Whenever a creature dies proliferate. (You choose any number of permanents
and/or players with counters on them, then give each another counter of a kind already there.)