Oath of Druids

At the beginning of each player's upkeep, that player chooses target player who controls more creatures than they do and is their opponent. The first player may reveal cards from the top of their library until they reveal a creature card. If the first player does, that player puts that card onto the battlefield and all other cards revealed this way into their graveyard.

During each player's upkeep, if that player controls fewer creatures than target opponent, the player may reveal cards from his or her library until he or she reveals a creature card. The player puts that creature into play and all other revealed cards into his or her graveyard.

Mystery Booster 2

Commander 2016

At the beginning of each player's upkeep, that player chooses target player who controls more creatures than he or she does and is his or her opponent. The first player may reveal cards from the top of his or her library until he or she reveals a creature card. If he or she does, that player puts that card onto the battlefield and all other cards revealed this way into his or her graveyard.