Promo card given away at Gencon 2015.
Mirrax is a new Boss that can be added to either Boss Monster or Boss Monster 2 giving more versatility to the boss deck.
Card text: "Level Up: Choose another Boss. For the rest of the game, this Boss also has that Boss's treasure icon. (The icon remains even if that Boss dies.)"
Foil version available in Boss Monster 2 Collector's Edition