Dweller of the Abyss

Menace, trample, double strike
Whenever Dweller of the Abyss deals combat
damage to a player put X +1/+1 counter on it,
where X is the damage dealt by Dweller of the
Abyss. All creatures you control gain power and toughness equal to the number of +1/+1
counters on Dweller of the Abyss.
You may remove X counters from Dweller of the
Abyss and cast a spell from you hand equal to
X.