Cheapest priced copy (Eventide): $9.49 at Card Kingdom, near mint, their price list as of .
Endless Horizons 
Enchantment · Rare · Eventide · #4
When this enchantment enters, search your library for any number of Plains cards, exile them, then shuffle.
At the beginning of your upkeep, you may put a card you own exiled with this enchantment into your hand.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $9.49 to $27.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eventide | 4 | Rare | $9.49 | $27.99 |
2 rulings from Wizards of the Coast
- 1 August 2008If Endless Horizons leaves the battlefield, the remaining Plains cards stay exiled. If Endless Horizons returns to the battlefield, it’s a new object with no relation to its previous existence. The previously exiled Plains cards will still stay exiled.
- 1 August 2008If a different player gains control of Endless Horizons, its ability will trigger at the beginning of that player’s upkeep, but it won’t do anything when it resolves.