Hei Bai, Spirit of Balance is a uncommon Legendary Creature — Bear Spirit card from Avatar: The Last Airbender (TLA), collector number 225. Current market price: $0.16 (foil $0.28), TCGplayer market prices via Scryfall.
Whenever Hei Bai enters or attacks, you may sacrifice another creature or artifact. If you do, put two +1/+1 counters on Hei Bai. When Hei Bai leaves the battlefield, put its counters on target creature you control.