From the publisher's website:

The DC Universe is in peril! In the DC Comics Deck-building Game Crisis Expansion, you will face some of the most epic challenges, events, and destructive forces in the history of comic-dom. But this time, you won’t be going in alone! The Crisis Expansion introduces co-operative gameplay and “Impossible Mode” for fans of the popular and critically acclaimed deck-building game. If you thought things were rough before, you ain’t seen nothing yet! The Crisis cards are for co-operative play only. Players must team-up to overcome these challenging events. The gameplay you thought you knew will never be the same when these ongoing terrors hit the table. Work together to defeat all of the Super-Villains before time runs out! The eight original Super Heroes and 12 original Super-Villains from the first set have been reimagined for the ultimate co-operative showdown. Crisis mode uses eight team-themed Super Heroes, Impossible Super-Villains, and a set of 15 Crisis cards, though not all of them are used every game, so you never know what might come up next. However, if you prefer to keep your deck-building competitive, there is a new set of SIX all-new Super Heroes and a slew of new main deck cards to keep your games as hard-fought as ever! Play Impossible Mode to make competitive play even more hard-core. Impossible Mode Super-Villains are much tougher than their lesser counterparts. You’ll beg for mercy when you are subjected to their new First Appearance Attacks, and marvel at the rewards you reap for defeating them... which is not easy!