Spellsaver

Cleric offering, Druid offering (You may cast this
card any time you could cast an instant by sacrificing
a Cleric and/or Druid permanent. If you do, the total
cost to cast this card is reduced by the total mana cost
of the sacrificed permanents.)
When you cast this spell, choose a number.
Spells you control with converted mana cost
equal to the chosen number can't be countered
this turn.