Fear My Authority is a common Ongoing Scheme card from Duskmourn: House of Horror Commander (DSC), collector number 333. Current market price: $0.70, TCGplayer market prices via Scryfall.
(An ongoing scheme remains face up until it's abandoned.) Creatures you control get +2/+2 and have fear. (They can't be blocked except by artifact creatures and/or black creatures.) At the beginning of your upkeep, abandon this scheme unless you discard a card or pay 3 life.