Bruvac the Grandiloquent is a mythic Legendary Creature — Human Advisor card from Secret Lair Drop (SLD), collector number 2181. Current market price: $54.29, TCGplayer market prices via Scryfall.
If an opponent would mill one or more cards, they mill twice that many cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)