Witness the most epic battle of all time in Crisis On Earth X, out now on DVD. To celebrate, we are giving two lucky readers the chance to win a copy of the four-episode crossover event set.

Barry and Iris's wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with the help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow, Supergirl, The Flash and White Canary - lead their teams into battle to save the world.

Crisis On Earth X stars Melissa Benoist (Glee), Mehcad Brooks (Supergirl), Chyler Leigh (Supergirl), Grant Gustin (Glee), Stephen Amell (Arrow), Emily Bett Rickards (Arrow), and Katie Cassidy (Gossip Girl), with Victor Garber (Argo), and Candice Patton (The Game).

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