Frostboil Snarl

As Frostboil Snarl enters the battlefield,
you may reveal an Island or Mountain card
from your hand. If you don't, Frostboil
Snarl enters the battlefield tapped.
{t}: Add {u} or {r}.
"A great smoke rose about us, vapor and steam.
Ice fell like rain as I threw down my enemy."
—Gandalf