The expansion's campaign has five matches; one against each of the new decks added to the game. Once all five have been defeated, the Revenge campaign will unlock, and you will face the same five decks again. This time, they will have more powerful cards and be tougher to defeat, but the challenge is not too great if you have unlocked a fair amount of cards during your time in the game.
Sepulchral Strength is the final deck of the revenge campaign. This deck does its damage by throwing out a lot of creatures with abilities that help increase their own power and toughness, or those stats for other creatures in play. The deck also has a moderate amount of creature removal spells and can make opponents discard.
I would recommend using a deck with a good amount of direct damage or creature removal spells. Make an effort to kill creatures as quickly as you can once the computer has put them on the board. This will keep the computer on the defensive and unable to build up a strong offense against you. I won easily using the Born of Flame deck.