Rotwood Planecaller

Rotwood Planecaller can't be countered
{3}{b}, {t}, Discard a card: Create a black Zombie Avatar creature token named Soulless One with power and toughness equal to the number of Zombies on the battlefield plus the number of Zombies in all graveyards. Activate this ability only as a sorcery.
The Rotwood is corrupted beyond recognition. Even the soul of the plane is broken.