Niv-Mizzet Reborn is a mythic Legendary Creature — Dragon Avatar card from War of the Spark (WAR), collector number 208. Current market price: $0.77 (foil $2.69), TCGplayer market prices via Scryfall.
Flying When Niv-Mizzet enters, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order.