Reaper of the Dead

Whenever a non-zombie creature dies, put a +1/+1 counter on a non-token zombie you control or put a 2/2 zombie onto the battlefield tapped.
{x}{b}{b}: Return all zombie creatures in your graveyard with converted mana cost X to the battlefield tapped. Activate this ability any time you could cast a sorcery and if Reaper of the dead is untapped.