Acnologia, King of Dragons

Hexproof, Annihilator 2
This creature is a Dragon in addition to its other types. When Acnologia enters the battlefield tap 3 Dragons you control, and if you do you may add one dragon creature from your library to your hand.
{5}{t}: Sacrifice a Dragon Creature you control, this creature gains +X/+X until the end of the turn, where X is that creatures power.