Rockslide

Rockslide deals damage to each creature without
flying and each planeswalker equal to the
number of Mountains you control.
Landfall — If you had a land enter the
battlefield under your control this turn, as an additional cost to cast this spell, you may
sacrifice a Mountain. If you do, Rockslide deals
damage to each creature and each planeswalker
equal to twice the number of Mountains you
control instead.