Cheapest priced copy (Magic 2015): $0.35 at Card Kingdom, near mint, their price list as of .
Glacial Crasher 
Creature — Elemental · 5/5 · Common · The List · #M15-57
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
This creature can't attack unless there is a Mountain on the battlefield.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic 2015 | 57 | Common | $0.35 | $0.49 |
| The List | M15-57 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 18 July 2014It doesn't matter who controls the Mountain.
- 18 July 2014If the only Mountains on the battlefield leave the battlefield after Glacial Crasher attacks, it stays attacking.