Sidisi, Aspiring Necromaster

Zombies you control have +1/+0 and Exploit (Whenever a Zombie creature enters the battlefield under your control, you may sacrifice a creature.)
Whenever a Zombie you control exploits a creature, exile X cards from your graveyard. Then, you may search your library for a card with converted mana cost less than or equal to X, reveal it, and put it into your hand.