Grimoire of the Dead is a mythic Legendary Artifact — Book card from Innistrad (ISD), collector number 226. Current market price: $0.96 (foil $13.94), TCGplayer market prices via Scryfall.
{1}, {T}, Discard a card: Put a study counter on Grimoire of the Dead. {T}, 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.