Cheapest priced copy (Khans of Tarkir): $0.49 at Card Kingdom, near mint, their price list as of .
Ivorytusk Fortress 
Creature — Elephant · 5/7 · Rare · Khans of Tarkir · #179
Untap each creature you control with a +1/+1 counter on it during each other player's untap step.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $1.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Khans of Tarkir | 179 | Rare | $0.49 | $0.49 |
| Khans of Tarkir Promos | 179 | Rare | — | $0.69 |
| Khans of Tarkir Promos | 179s | Rare | — | $1.79 |
3 rulings from Wizards of the Coast
- 20 September 2014Each creature you control with a +1/+1 counter on it untaps at the same time as the active player’s permanents. You can’t choose to not untap them at that time.
- 20 September 2014Effects that state a creature you control doesn’t untap during your untap step won’t apply during another player’s untap step.
- 20 September 2014Controlling more than one Ivorytusk Fortress doesn’t allow you to untap any creature more than once during a single untap step.