Taysir of Rabiah

{x}{u}{u}{u}, {t}, Sacrifice Taysir of Rabiah:
Destroy X target Mountains. Taysir of Rabiah
deals X damage to each creature and player.
If Taysir of Rabiah would leave the battlefield,
you may pay {3}{w} to have it become an exact
copy of any white creature in play instead. The
same goes for {3}{u} and blue creature, {3}{b} and
black creature, {3}{r} and red creature, and
{3}{g} and green creature.