The Flavormancer is a mythic Legendary Creature — Hero Villain card from Unknown Event (UNK), collector number MZ01a.
Before the game begins, if The Flavormancer is your commander, legendary creature and planeswalker cards in your deck that are flavorfully Heroes or Villains gain that creature type. (For example, Gideon becomes a Hero and Yawgmoth becomes a Villain. Yes, planeswalkers get creature types this way. Don't worry about it.) Once during each of your turns, you may cast a Hero or Villain spell from your hand without paying its mana cost.