Mystic Enforcer is a special Creature — Human Nomad Mystic card from Time Spiral Timeshifted (TSB), collector number 96. Current market price: $0.34 (foil $4.50), 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.