Fafnir, Abyssal Tyrant

Flying
At the beginning of your upkeep, each player puts the top X cards of their library into their graveyard, and each opponent loses X life, where X is the number of Zombies you control
{u}{b}{g}{t}, Sacrifice another Zombie: Create X 2/2 Zombie creature tokens onto the battlefield, where X is the sacrificed Zombie's power