Hearthpwn

Figured I'd share the meme dream Priest deck that carried me from rank 5 to Legend this month (still dumpster tier in Standard Legend I know, but as you can see above, I'm also in Wild legend, so my time was divided this month).

I went 38-13 in the last 51 games from rank 5 to legend, working out to a 74.5% winrate.

Anyway, the deck is pretty straightforward: drop fat minions, buff & then copy them with Shamblers, and then go face when you can ko the opponent. 

Play Style

Typically, Priest is viewed as a slow class which only reacts, failing to take initiative. Well, not here. In fact, if you haven't won the game by turn 10, you've probably lost.

With this deck, what you want to do is stall for time during the first few turns, usually trading with your opponents' minions to keep them from snowballing to victory before you amass the combo. All of your minions have very high health (which you can make higher easily) so trading will be very favourable for you. 

Once you approach turns 5-8, you will hopefully have a couple decent-sized minions on board, and enough spells in hand to create a monster to go for lethal.

Your Minions (new)

Northshire Cleric will win you games when used smart. Don't just throw one down Turn 1 if it isn't going to draw you anything before it dies. For example, against a Druid who is likely holding Wrath, this is a poor play. On the other hand, against Paladin, Turn 1 Cleric is a great play, since they have no early removal, and it denies them their Hero Power (or else they give you a free card after trading Cleric into Recruit). If you're going second, Turn 1 Cleric + Coin + PW: Shield is a strong opening play if you don't have a Turn 2 play in hand (Ancient Watcher). And of course, we have 2 Circle of Healings to combo with the Clerics, which I will get into in the Combos section.

Ancient Watcher, Humongous Razorleaf, and Injured Blademaster are your core targets for buff spells. Play these as soon as you can, since most of your spells are dead cards in hand with no friendly targets on board.

One major mistake to avoid: Do not play Ancient Watcher + Silence on Turn 2 (1 with Coin), or Humongous Razorleaf + Silence on Turn 3 (2 with Coin). The reason? Because there is no point in silencing these minions the turn they are played, since they still cannot attack until the following turn. If you pre-silence, you run the risk of having them Hexed, bounced back to hand, or otherwise destroyed, and now you've lost 2 cards instead of 1, including a crucial combo enabler in Silence. A Turn 4 Ancient Watcher + Purify is much less risky, since the Purify will at least cycle itself, unlike Silence.

Faceless Shambler is perhaps the strongest card in the deck. While a 20/20 Razorleaf is impressive and scary, it is not immune to single target removal like Hex or Execute. Duplicating a 20/20 with Shambler not only increases your chance of having lethal next turn, but also reduces the risk of having all your eggs in one basket. It also shuts down aggro hard, of course.

Radiant Elemental and Kabal Talonpriest serve obvious functions, reducing the cost of combo cards, and providing additional health buffs before Inner Fire. 

Auchenai Soulpriest is here just for when all hope is lost on board and you need a hard reset. 4 damage aoe clears just about everything relevant (all Pirate Warrior minions have <4 health). It can also be used as a buff target.

Lyra the Sunshard provides extra value, lots of cheap spells to set her off.

Your Spells

Most of them are self-explanatory so I won't get into too much detail right now.

Mass Dispel is the only standout in the list. This is your key to victory against Taunt Warrior. Your opponent could have 7 Taunts while you only have one 20/20 plant, but with Dispel, you don't care. This is half the reason why you don't need to waste precious spots in the deck with cards like SW: Pain and Death.

Note: I originally ran Embrace the Shadow in this deck, but more often than not, it lost me games simply by being one of the three choices offered by Shadow Visions instead of something I really needed to win the game, like Divine Spirit. Running Auchenai instead alleviates this issue.

Combos 

Cleric(s) + CoH: you can easily draw 6+ cards in one turn with this play. Don't be afraid to awkwardly trade into your opponents' minions to increase the total number of minions healed. The sooner you can get 2 Divine Spirits + Inner Fire, the better. If you have 2 Clerics on board and there are 4 damaged minions, you just got yourself 8 cards! (make sure not to overdraw though, you can't afford to lose a Divine Spirit).

Radiant Elemental + Spells: You can cheat out a lot of mana in this deck with this guy, since almost all of your spells are 2 mana or less. A strong Turn 2 (Turn 1 with Coin) play is Radiant + PW: Shield (which costs 0 now). 

Cleric + Blademaster + CoH: This is pretty obvious.

Humongous Razorleaf + Faceless Shambler: will ideally you have something like a silenced 4/20 leaf to copy with Shambler, sometimes you don't draw cards in the right order. For instance, you may get Razorleaf out on turn 3, have no silence cards for turn 4, but have PW: Shield, Talonpriest, Inner Fire, and Shambler/Sunfury in hand. In this case, don't be afraid to spend buffs on an unsilenced minion. Make that Razorleaf into a 13/13 and copy it with Shambler on Turn 5/give it taunt with Sunfury Protector against aggro. Just don't forget that it isn't silenced; you don't want to get overexcited and create a 26/26 minions, realize it needs to be silenced to attack, and suddenly be stuck with a 4/8 no-taunt plant. 

PW: Shield, Talonpriest + Divine Spirit: Whenever possible, play Divine Spirit last. In case math isn't your strong suit: Razorleaf + PW: Shield + Talonpriest + Divine Spirit = 4/26, while Razorleaf + Divine Spirit + PW: Shield + Talonpriest = 4/21.

Mulligan Guide 

Honestly, this deck probably has the simplest mulligan strategy you've ever seen. In all games, against any class, you:

1. Throw every spell away (except i) PW: Shield if you also have Radiant Elemental or Cleric and going second, or ii) Purify if you're also holding Ancient Watcher and going Second).
2. Keep Northshire Cleric, Ancient Watcher, Humongous Razorleaf; consider keeping Radiant Elemental if it's the only minion you have/nothing else to play Turns 1/2. 
3. Throw Auchenai, Lyra, and Shamblers away 
4. Keep Talonpriest if you have Cleric, Watcher, or Radiant to land buff on. Otherwise toss.
5. Keep Sunfury Protector if you think your opponent is hyper aggro (Pirates, Murlocs).

Why throw the spells away? Because you have Shadow Visions to find them/add more of them to your deck. For example, if you kept Divine Spirit in hand, and then Turn 1 you draw the other Divine Spirit, then that's it, you have 2 Divine Spirits all game. Now suppose you throw all the spells back, have only minions in hand, and Turn 1 you draw Shadow Visions. Great, now you can discover Divine Spirit! In this way, you increase your odds of getting more than 2 of the key cards throughout the game.

In the special cases of keeping spells above, the scenarios play out as i) Turn 1: Coin + Cleric/Radiant + PW: Shield or ii) Turn 1: Coin + Ancient Watcher, then Turn 2: Purify + attack. These scenarios are your quickest ways to gain board control, but are not necessary to win & should not be searched for in mulligan because it will increase your risk of drawing cards like Divine Spirit too early.

Replacements

Lyra the Sunshard: while unique, she isn't critical to the deck, as I've rarely got any spells out of her that were game-winning., and sometimes it's hard to generate any value out of her. So you can easily substitute this with another Injured Blademaster (which combos well with Northshire Cleric+Circle of Healing).

Shadow Visions: this is too good to replace, just craft both. It's like having 4 Divine Spirits in your deck. 

Faceless Shambler: Faceless Manipulator (but you'll need to add another Sunfury Protector to give them Taunt to survive against aggro, so not ideal.

Since it's been asked, Purify: Honestly, it's kind of the whole point of the deck, to utilize huge, over-statted minions by removing their one downfall (can't attack). Kabal Songstealer is slower but probably the closest substitute. If you don't have this, I'd probably replace them with other spells like SW: Pain or Holy Nova (this would dilute your Shadow Visions pool though). I'd also remove 1 or 2 silence-needing minions for another Injured Blademaster and maybe a second Sunfury Protector. I doubt the deck would perform nearly as well, though.

Match-Up Advice (new)

Pirate Warrior: Getting an Ancient Watcher/Razorleaf/Blademaster down by turn 3 is crucial. If you can make a 4/16ish Taunt with Shambler/Sunfury with your hero still at 9+ health (out of range of 2 Mortal Strikes), you should be fine. Don't waste time/mana playing cards like Purify if you have health buffing/taunt options to play instead; it's more important to build a wall than attack. Auchenai + CoH also shines in this match-up; save it for when they have 2-3 good targets like Frothing, Cultist, Captain, and/or Kor'Kron. Use Cleric and Radiant to trade with their 1/1 pirates to deny weapon upgrade via Cultist.

Aggro Druid: Almost the same as Pirate Warrior. However, even more so than Pirates, you want to keep their board clear since 1-2 Savage Roars could clear your wall quickly. Prioritize killing beasts to deny card draw from Mark of Y'Shaarj. They'll run out of steam by turn 6 or so, so just try to stabilize by then; 9+ health is the magic number again, out of range of double Swipe to the face.

Quest Rogue: This is a pretty even match-up, mostly depending on their start. Play Silence offensively on their Igneous Elemental to slow them down. Beware of Vanish; don't go all in with your buff spells unless you can make lethal on the same turn.

Miracle Rogue: Honestly find this to be one of the easiest match-ups. Unless they run Sap (which I rarely encountered), there's nothing they can do to your huge minions. You can also Silence Sherazin to end those shenanigans. 

Quest Warrior: This is where you can get a lot of value out of Cleric + CoH. Quest Warrior often has a couple low attack, high health minions on board, so go ahead and ping them to draw extra cards. Try to keep 2 minions on your side of the board at all times, and try to evenly split your buffs between them, since an Execute could ruin your day at any moment if you invest solely in one minion. Having 2 minions out also increases your likelihood of winning Brawls, while not overextending. You're gonna have to play relatively aggressive in this fight, since their quest will spell doom for you. Plan to win around Turn 8-9 by Mass Dispelling their Taunts and sending everything face.

Freeze/Quest Mage: Like Quest Warrior, the sooner you can win the better. Don't wait for the perfect minion; start beating on their face with a 16/16 Cleric on Turn 4 rather than building up a 40/40 Razorleaf by Turn 7. You need to pop their Ice blocks fast. Your secret weapon in this fight is Silence/Mass Dispel. Their common response to your big board is Frost Nova + Doomsayer. All you need to do is throw a Silence on the Doomsayer and you're good to go. So use your Purifies on your own minions, and save Silence for offensive plays here. Primordial Glyph can be a pain when they find Polymorph or Meteor, so work on making at least a 4/20 minion and copying it with Shambler so they can't remove everything. Additionally, if the Mage is down to 1 health and freezes your board, you can silence any one of your minions to remove the freeze effect and go face to pop Ice Block/kill them. 

Murloc Paladin: An early Cleric is great here, as it denies them their Hero Power. Trade fast and often; the less Murlocs on board when they play Gentle Megasaur, the better. If they get the Poisonous adapt, you're just kind of screwed. Mass Dispel can be used to remove all of the buffs/auras, so use it wisely. Of course, there's nothing you can really do if they draw Sunkeeper Tarim or Equality; just don't play too many minions at once, so you can potentially recover. 

Midrange Hunter: Pretty similar to Murloc Paly, you want to keep their board clear to deny beast synergy. Unless they run Hunter's Mark/Black Knight, there's nothing they can do against a 20/20 taunt minion, so just play slow and steady. After they use up their Kill Commands, all they can do is Hero Power your face for 2, which you can simply undo on your turn with your own HP. Feel free to throw a Silence on their Highmane to make cleaning up the board easier.

Shaman/Warlock: I barely saw these on ladder/were easy wins. Shaman is either aggro or elemental, but either way, just play around Hex/Devolve and you're good. Warlock is probably zoo, so just clear their tokens and let them kill themselves with Life Tap. 

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I'll write a more thorough description if this gets 25+ upvotes. Cheers.

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4/27/17 Update 1: Thanks for the positive feedback everyone. I've written several new sections and expanded on some old ones. 

If this gets to 50+ upvotes, I'll finish it off with a strategy guide on how to play against the most common meta decks. 

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4/30/17 Update 2: Front page woot. Added the match-up advice. Think I covered most relevant decks, ask in comments if I forgot one you wanna know about.