C'thalpa, The Internal One

When C'thalpa, The Internal One enters the battlefield from anywhere other than the exile
zone, exile it.
When C'thalpa, The Internal One enters the battlefield or attacks, destroy target land.
{3}{r}{r}{r}: Return C'thalpa, The Internal One
from exile to the battlefield tapped. Activate this ability only if a player has 5 or more lands in his
or her graveyard.