Nyvru, The Apocalypse Dragon

Indestructible, Flying, Trample
Nyvru cannot attack, block, or activate abilities unless it has five or more charge counters on it
Whenever a player loses 3 or more life in a turn, put a charge counter on Nyvru
Whenever Nyvru attacks, Destroy target creature. Nyvru deals damage to that creature's controller equal to it's toughness
{2}{b}{r}{t}: Destroy target Permanent