Dark Growth Mage

Giant Slayer (If this creature deals damage to another creature that has 8 or more toughness, the damaged creature is destroyed)
{t}: Grant +0/-X to all ally creatures. On your next upkeep step. remove this counter and instead grant all those creatures +0/+X. X can be any number.
Damage dealt by Dark Growth Mage is instead dealt as a +0/-X. On the creatures next upkeep step, instead grant it +0/+X, X being the damage dealt.