Niv-Mizzet, Supreme is a rare Legendary Creature — Dragon Avatar card from March of the Machine: The Aftermath (MAT), collector number 219. Current market price: — (foil $6.22), TCGplayer market prices via Scryfall.
Flying, hexproof from monocolored Each instant and sorcery card in your graveyard that's exactly two colors has jump-start. (You may cast that card from your graveyard by discarding a card in addition to paying its other costs. Then exile it.)