Mass murder

You may put a creature card from your hand onto the battlefield. If you do, sacrifice it unless you pay its mana cost reduced by .

, , Discard a card: Put a study counter on Grimoire of the Dead. , Remove three study counters from Grimoire of the Dead and sacrifice it: Put all creature cards from all graveyards onto the battlefield under your control. They're black Zombies in addition to their other colors and types.

Flying When this creature enters, exile all Zombies, then return all Human creature cards from your graveyard to the battlefield.