Mystic Enforcer is a uncommon Creature — Human Nomad Mystic card from Dominaria Remastered (DMR), collector number 360. Current market price: $0.17 (foil $0.55), TCGplayer market prices via Scryfall.
Protection from black Threshold — As long as there are seven or more cards in your graveyard, this creature gets +3/+3 and has flying.