Hunting Goliaths

Fixed Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep step, you may cast this card from exile without paying it's mana cost. X will be what X was originally cast for.)
All creatures below the converted mana cost of X gains +2/+3 whilst all creatures above the converted mana cost of X gains -2/-3.