Hi! I wanted to provide further explanation on how the Sealed Campaign will work in Magic 2014 – Duels of the Planeswalkers:
The game will come with two available slots for players to start Sealed Campaigns. These slots will keep all the deck edits and additions you make, plus your progress though the Sealed Deck Campaign. If you’d like to save more than two Sealed Decks, additional slots can be purchased for $1.99 each, and each slot will give you access to a different pool of cards and allows you to unlock different boosters. All Booster Packs use cards from a 151 card “set” that’s unique to the game (consisting of 10 mythics, 29 rares, 51 uncommons, and 61 commons). To begin a Campaign, players will pick an open slot and get six 14-card Booster Packs to open. Players are then taken to the Deck Editor so they can create a 40-card Sealed Deck out of the 84 card pool they’ve opened (plus Basic Lands).
When finished creating a deck, players can then battle their way through the Sealed Deck Campaign in order to unlock an additional three Booster Packs along the way. At the end of the Campaign there will be a boss fight where the player will play to defeat another Sealed Deck. You can also use your Sealed Decks to play against other players.
EDIT: There's been a correction on the size of the Sealed card pool (was 180+, is now 151), plus I've added the allocation of the various rarities. Sorry for the confusion.
EDIT AGAIN: Additional details in this response post.