From the Wizards website…
The Innistrad and Dark Ascension sets showed us a world where humanity is beset on all sides by monsters, including vampires, zombies, and werewolves. Avacyn, a living covenant whose angelic powers protected humans, was imprisoned within the Helvault and feared lost forever. But just as humanity’s darkest hour beckons, Avacyn is freed, inspiring hosts of angels to usher in a new dawn. But even though they no longer have the upper hand, the creatures of the night are still a dangerous threat. The eternal struggle on Innistrad continues in this thrilling conclusion.
Don’t confuse this new dawn with a complete victory for humanity. Innistrad’s horrors have suffered a blow, but they still command unspeakable evil and power. If your decks favor the more unsavory denizens of Innistrad, you’ll find plenty of ways to torment the opposition. Will you follow Avacyn’s lead, Planeswalker, and marshal your powers for good? Or will you use the still potent weapons of the night in your quest for supremacy?