Sarcha, Lavashaper

{r}{r}{r}, {t}: Target Mountain you control
becomes a 4/4 red Elemental creature with
lavatouch 1. It's still a land. (Whenever it deals
damage to a creature, put a -1/-1 counter on that
creature. Then add {r}. You don't lose this mana as
steps and phases end.)
Whenever a Mountain you control deals damage
to a player, exile the top card of your library. You
may play that card this turn.