Shirei, Shizo's Caretaker is a rare Legendary Creature — Spirit card from Betrayers of Kamigawa (BOK), collector number 81. Current market price: $1.05 (foil $46.33), TCGplayer market prices via Scryfall.
Whenever a creature with power 1 or less is put into your graveyard from the battlefield, you may return that card to the battlefield at the beginning of the next end step if Shirei is still on the battlefield.