Cheapest priced copy (The List): $0.59 at Card Kingdom, near mint, their price list as of .
Leonin Relic-Warder 
Creature — Cat Cleric · 2/2 · Uncommon · Mirrodin Besieged · #10
When this creature enters, you may exile target artifact or enchantment.
When this creature leaves the battlefield, return the exiled card to the battlefield under its owner's control.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.59 to $8.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2017 | 65 | Uncommon | $0.69 | — |
| Mirrodin Besieged | 10 | Uncommon | $0.69 | $8.99 |
| The List | C17-65 | Uncommon | $0.79 | — |
| The List | MBS-10 | Uncommon | $0.59 | — |
One ruling from Wizards of the Coast
- 1 June 2011If Leonin Relic-Warder leaves the battlefield before its first ability has resolved, its second ability will trigger and when it resolves, do nothing. Then its first ability will resolve and exile the targeted artifact or enchantment with no way to return it to the battlefield.