Cheapest priced copy (Commander Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Shirei, Shizo's Caretaker 
Legendary Creature — Spirit · 2/2 · Rare · Betrayers of Kamigawa · #81
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.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.35 to $29.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Betrayers of Kamigawa | 81 | Rare | $1.49 | $29.99 |
| Commander Masters | 186 | Uncommon | $0.35 | $0.49 |
| Commander Masters | 676 | Uncommon | $0.59 | $1.49 |
| Ultimate Masters | 112 | Uncommon | $0.35 | $0.79 |
4 rulings from Wizards of the Coast
- 7 December 2018Shirei'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.
- 7 December 2018Shirei's ability triggers if a creature you own with power 1 or less dies under another player's control.
- 7 December 2018If 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.
- 7 December 2018Shirei's ability can't return any creatures that died before Shirei entered the battlefield.