Centaur Chieftain is a uncommon Creature — Centaur card from Eternal Masters (EMA), collector number 160. Current market price: $0.15 (foil $0.33), TCGplayer market prices via Scryfall.
Haste Threshold — As long as there are seven or more cards in your graveyard, this creature has "When this creature enters, creatures you control get +1/+1 and gain trample until end of turn."