Sundering Balestorm

As Sundering Balestorm enters the battlefield,
exile target permanent with a mana cost equal to {x}, gain that much life.
If {x} is ten or more, exile {x} permanents of mana
cost {x} or less, gain life equal to mana cost of each permanent exiled this way.
Each time a permenent leaves the battlefield from
an ability, spell, or dies from a creature you
control, gain life equal to its mana cost.