Thrummingbird is a uncommon Creature — Phyrexian Bird Horror card from Phyrexia: All Will Be One (ONE), collector number 72. Current market price: $0.29 (foil $0.30), TCGplayer market prices via Scryfall.
Flying Whenever this creature deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)