Keeper of Keys is a rare Creature — Human Rogue Mutant card from Conspiracy: Take the Crown (CN2), collector number 34. Current market price: $4.11 (foil $5.36), TCGplayer market prices via Scryfall.
When this creature enters, you become the monarch. At the beginning of your upkeep, if you're the monarch, creatures you control can't be blocked this turn.