From the publisher's website:

Check out the Legendary Guardians of the Galaxy Expansion for the Legendary® Deck Building Game! This expansion consists of 100 all new playable cards and a Color Rule Sheet. The content consists of 5 heroes, 2 new villain groups and 2 Masterminds. Find all new original art featuring 4 pieces of unique art per hero! This is not a standalone product, a Core Set (including Villains) is required for game play. Guardians of the Galaxy is easy to learn and features incredible original artwork of Marvel Heroes and Villains. Players can create their own powerful combos on the fly, combining their hero's awesome abilities to take down the Marvel Masterminds. Legendary® Guardians is a fast paced game full of strategy, depth, fun and replay-ability. Innovative Mastermind mechanics allow the game itself to fight back against the players.