Perimeter Enforcer is a uncommon Creature — Human Detective card from Murders at Karlov Manor (MKM), collector number 31. Current market price: $0.10 (foil $0.22), TCGplayer market prices via Scryfall.
Flying, lifelink Whenever another Detective you control enters and whenever a Detective you control is turned face up, this creature gets +1/+1 until end of turn.