Shirei, Shizo's Caretaker
Legendary Creature — Spirit
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, Shizo's Caretaker is still on the battlefield.
Illustrated by
Betrayers of Kamigawa#81RareEnglishLegality
Rulings
Shirei’s ability only triggers if the creature’s power immediately before leaving the battlefield is 1 or less, regardless of its power in your graveyard.
Shirei’s ability triggers if a creature you own with power 1 or less dies under another player’s control.
If Shirei leaves the battlefield and returns to the battlefield after a creature with power 1 or less is put into your graveyard, Shirei is considered a new object. The delayed triggered ability won’t return the creature to the battlefield.
Shirei’s ability can’t return any creatures that died before Shirei entered the battlefield.