Dark Petition is a rare Sorcery card from Magic Origins Promos (PORI), collector number 90p. Current market price: $6.19 (foil $6.56), TCGplayer market prices via Scryfall.
Search your library for a card, put that card into your hand, then shuffle. Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, add {B}{B}{B}.