Baku Altar is a rare Artifact card from Betrayers of Kamigawa (BOK), collector number 152. Current market price: $2.15 (foil $4.48), TCGplayer market prices via Scryfall.
Whenever you cast a Spirit or Arcane spell, you may put a ki counter on this artifact. {2}, {T}, Remove a ki counter from this artifact: Create a 1/1 colorless Spirit creature token.