Hearthpwn

Hello, I'm TaikiM13 and thank you for viewing my deck! I made it to legend with Priest this season again and I wanted to share the deck with you guys. I stream at http://www.twitch.tv/taikim13/ so check me out if you want ^^

EDIT: Updated with Mulligan guides

It's a pretty standard Priest deck, with some interesting techs.
This deck has a great matchup against aggro decks, druid, paladin, warrior, and most variants of control. Rogue and Handlock is hard for any priest deck, but I've tried to include counters for Rogue like Loatheb and Harrison Jones.

EDIT: I see a lot of comments stating that some people are having trouble with this deck against aggro. Against aggro, you have to mulligan very hard for board clears and early game drops. You clear a board against aggressive decks once and they can never recover. Against midrange decks like paladin, you have to be very greedy with your board clears. try to Auchenai+Circle 4+ minions, not just two. Try to keep Pyro as long as you can to counter Muster. Of course, sometimes you can't be as greedy with your board clears as you want, but the key to playing priest is knowing when to be conservative and when to put minions on the board. Priest does not have the easiest learning curve so don't be discouraged if you lose a few games here and there.

Harrison is in here to beat Rogue and make the Paladin match-up easier. It also makes the good Warrior match-up even better. Loatheb is also in here because of Rogue and because of his good body. 

Double Cabal is in here because when I was climbing, I was facing a lot of midrange decks. And with the popularity of Demonlock and Shaman, stealing a Nerubian Egg or any small minion for free is very devastating for the opponent.

Dr Boom is Dr Boom. Too Good.

Mulligans:

Hunter: Keep Northshire Cleric, Power Word: Shield, Wild Pyromancer, Holy Smite, Zombie Chow.
If you have Circle of Healing in hand, mulligan it unless you have Auchenai Soulpriest or Injured Blademaster with it. Keeping Sludge Belcher is okay if you alredy have early game plays.

Mech Mage: Keep Northshire Cleric, Power Word: Shield, Wild Pyromancer, Zombie Chow, Holy Smite, Circle of Healing, Injured Blademaster(only with circle,cleric,or early game), and Auchenai Soulpriest. Board clears are very important

Druid: Keep Thoughtsteal, Auchenai Soulpriest, Circle of Healing, and Injured Blademaster.
Keep Northshire Cleric only if you have Power Word: Shield in hand or the Blademaster+Circle combo.

Warrior: Keep Harrison Jones, Loatheb, Thoughsteals, 4-drop minions.

Rogue: Keep Injured Blademaster, Auchenai Soulpriest, Harrison Jones, Loatheb, Circle of Healing. Keep Northshire Cleric only if you have Power Word: Shield in hand or the Blademaster+Circle combo. Be greedy with Auchenai+Circle. That combo is one of the only ways Priest can ever gain board control in this match-up.

Shaman: see Mech Mage

Priest mirror: Keep Auchenai Soulpriest, Injured Blademaster, Circle of Healing, Loatheb, Sylvanas Windrunner, and Thoughtsteal. 

Warlock: see Mech Mage

Paladin: Keep Northsire Cleric, Power Word: Shield, Injured Blademaster(only with circle), Auchenai Soulpriest, Zombie Chow,  Wild Pyromancer, and Harrison Jones.

 EDIT: Took out a Sen'jin Shieldmasta for a Zombie Chow to improve the Hunter match-up and against other aggro decks. 

EDIT 2: With the increase of Paladins, Druids, Demonlocks, and Warriors, I substituted a Zombie Chow for The Black Knight.

 Replacements:

For Harrison Jones and Vol'jn, Acidic Swamp Ooze if you really want that weapon destruction, The Black Knight, Zombie Chow, or second Shadow Word: Death