Hearthpwn

This deck is constructed out of two main mechanics, card draw and deck. Use the various means of card draw to obtain board clear cards like Excavated Evil and Entomb as you want to play Brann + Benedictus to play your opponent's good cards. I found Shadow Visions very helpful for getting copies of Excavated Evil (against Murloc decks) and Entomb (deck-important minions like C'Thun).*

As you're including Prince Malchezaar and later your opponent's minions from Benedictus, this deck is also viable for Amara and N'Zoth. As of writing this, in the last game I played, I had N'Zoth summon Toshley (Malchezaar), Deathlord, and Loot Hoarder to complete the 7; the 4 deathrattle minions I summoned earlier were those 3 plus another Toshley from Shadow Essence which itself came from Lyra the Sunshard.

Speaking of Lyra, optimally you want to play both Radiant Elementals, Lyra, and 1 Shadow Visions (the other being in your deck) for 9 mana (or less if you played Thaurissan before), which will allow you to play spells constantly until your time runs out and fill the rest of your hand with Priest spells. Even if you don't manage to play this combo, Lyra + any spell is still value, given that the only spells in this deck are Power Word: Shield, Shadow Visions, Mass Dispel, Excavated Evil, and Entomb. However you play Lyra, you should have played enough spells by the time Yogg-Saron comes around.

A caveat: if your opponent also has Benedictus, hypothetically you and your opponent can both play Benedictus repeatedly if one of you obtains Benedictus from Benedictus. You don't want to do this, especially in late game, since neither of you will fatigue and the game will result in double defeat after 90 turns.

I could have included Coldlight Oracle, but one of the strengths of this deck is that your hand will be almost full for most of the game and thus you don't want your opponent to have the same.

Last but not least, Elise the Starseeker serves as the final win condition, especially if you play the Golden Monkey after playing Benedictus, in which case you'll have a hand and deck full of legendaries that are larger than your opponent's.

*Assuming the only spell you've received in your hand is 1 Shadow Visions, you have a 50% chance of discovering Excavated Evil or Entomb.