Glacial Crasher
Creature — Elemental
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Glacial Crasher can't attack unless there is a Mountain on the battlefield.
5/5
Illustrated by
Magic 2015#57CommonEnglishLegality
Rulings
Jul 18, 2014
It doesn’t matter who controls the Mountain.
Jul 18, 2014
If the only Mountains on the battlefield leave the battlefield after Glacial Crasher attacks, it stays attacking.