Hearthpwn

Intro

Working on a build for an OTK priest. Takes a while to set it up, but the base combo itself only requires 6 cards in hand. Probably easier in wild though. The idea is to gather set pieces to play an OTK with your upgraded hero power (HP) Mind Shatter (the combo could also double as a full self-heal if you have your starting hero power :P)

Main reason for this is so grinding gold priest portrait will be very satisfying. The second reason is that there are already cool OTK priest options with cards that I do not own (as most of us probably won't) on one account (like Malygos,Lyra the Sunshard, Shadowreaper Anduin). So I figured it might be cool to have an alternative version - albeit it a bit cheaper. Even Bloodmage Thalnos is not a necessity in this deck for the combo itself, which could bring the total cost down to 5600ish dust.

In short, this is for ppl that love to surprise the meta and hit your opponent's face for 48 with a HP (+ 32 dmg Holy Smites) as a priest, instead of a hunter/warlock. If your first thought is to replace 2 x Shadowform with 2 x Mind Blast, I'd just recommend something like Disguised Toast's OTK priest: https://www.hearthpwn.com/decks/1100120-disguised-toast-otk-priest.

Gameplay

Idea is to reach the following conditions:

1. Kill off (at least) one Clockwork Automaton, Prophet Velen, Radiant Elemental
2. Try to get 2 Vivid Nightmare and Shadowform via Shadow Visions or draw
3. Play 2 Shadowform so your HP is upgraded to Mind Shatter (remember: this spell renews your HP, so you can maximise its value from turn 7 by healing for 2, switching and then dealing 2 dmg)
4. Save 2-3 x The Coin from Gilded Gargoyle depending on draws
5. Upgrade Greater Diamond Spellstone to max
6. Survive until you meet all these conditions

There are many combo options, but the strongest one is the following: Play your Greater Diamond Spellstone alongside a Radiant Elemental. If you're lucky, you will get a Clockwork Automaton, Prophet Velen, Radiant Elemental and a random minion for 8 mana. Then play 2 x The Coin to pay for at least 2 x Vivid Nightmare (1 mana each with 2 elementals on board) on Prophet Velen and your HP (2 mana) for 48 dmg. And, if you have them, hit face with two Holy Smites for 32.

The more tricky option is to play the spellstone standalone (get at least Velen, Automaton and a Radiant Elemental) and then have enough coins for 2 x Vivid Nightmare and 1 HP (6 mana on top of the spellstone = 3 x The Coin in hand). You get two chances to do this since you have two Greater Diamond Spellstone. Divine Hymn is here to stall against aggro until Psychic Scream/big Spirit Lash, or to heal up your Vivid Nightmare copies in case you lack mana or coins for a HP on a combo turn ... and hope they don't wipe your board until your next turn :P

Example

In total you should have at least 4 HP doubling cards on board (in any combination of Clockwork Automaton and Prophet Velen) and an upgraded HP to reach the 48 dmg OTK (or 32 dmg with Aunduin if you're running him.) If you plan on just using your HP to land lethal, copying/ressing Clockwork Automaton is okay.

If you also have 2 x Holy Smite in hand, as said above, copy Prophet Velen for an additional 2*2^(amount of Velens on board) = 4-32 dmg on top of your HP dmg. So the dream would be 48 dmg from HP and 32 from Holy Smite for a total of 80 dmg. Which is ridiculous, I know. Either way, it should look something like this:

Even without shadowform (3 dmg base) it still packs a punch. With shadowform it would be 48 dmg total with 4 multipliers on board. If the two spells in hand were Holy Smite, this would be even sicker.

Satisfaction!

Mulligan

Against aggro I would suggest sticking to Bloodmage Thalnos, Holy Smite (for those pesky Imps) and Spirit Lash (against paladins'n such). Don't hesitate to kill off Bloodmage Thalnos with an early Spirit Lash if you have Twilight's Call and a second Spirit Lash in hand. Just remember that every minion you hit will heal you for 2. Just be mindful of turn 5 plays (Level Up!, Fungalmancer, Wargear) and clear the board beforehand if you feel something big is coming.

If it turns into more of a midrange game, use Shadow Visions to fish for Psychic Scream before turn 7. If you happen to draw Prophet Velen or Clockwork Automaton, just play them for tempo. If they happen to survive, you can always use your upgraded HP to heal or even drop a Vivid Nightmare if you're lucky. In most cases, you just have to make sure you outlast the early game. Then it's usually a won game.

Against control just make sure you get your minions to die asap. Best is probably to mulligan for Radiant Elemental in combination with Shadow Visions and Power Word: Shield, so you can start gathering your combo on turn 2/3. Control decks will be able to remove pieces most of the time anyway, so just focus on trying to get the full combo in hand and your HP upgraded (48 dmg max) asap. Just be mindful of transform effects. Use the 2nd Automaton to bait out Polymorph or Hex (which will also dilute your res pool.) If you can, do not play Bloodmage Thalnos to increase your OTK odds. Also try to save your Holy Smite for additional combo dmg against Warriors and Druids (no transform issues in these matchups!)

Against other combo decks just try to dig for your draw cards and get in as much chip damage as possible, it's just a race against the clock. If you can, drop your big minions on a board that's being prepped with a Doomsayer, to avoid transforms or gain some tempo with your spellstone.

Substitutes

Obviously extra minions make the resurrect a bit trickier, so you can ditch a redundant minion if you want higher res chances. You just need the coins and dmg multipliers. So Bloodmage Thalnos is actually the most risky minion of the deck, but can be handy when trying to increase draw or to fend off aggro decks in combination with Spirit Lash. If you lack the dust to craft him, you can just substitute him for a Loot Hoarder or another Holy Nova.

Instead of Bloodmage Thalnos and a Mass Dispel, it could be also possible to run 2 Gadgetzan Auctioneer, to use with any spare coins and your cheap spells. Or swap them with just two draw/healing cards (preferably spells) to draw faster or stall the game, respectively. 

You could also consider replacing a Mass Dispel with the Awaken the Makers. The quest is probably not the best fit, given that the quest reward also dilutes the pool. I don't own Zerek's Cloning Gallery on either of my accounts sadly, but I'm sure that could also be a great addition to this deck.

Shadowreaper Anduin is also a nice sub for Shadowform. You can't fish him with Shadow Visions though, but he's very powerful. I tried playing these separate and together in the deck. If anything I'd suggest picking one of the two options for a HP upgrade. If you drop both Shadowform cards, you can consider another copy of a healing spell like Divine Hymn.

Last but not least, you could in theory play this deck without either Prophet Velen or Clockwork Automaton, but then your max combo option on an empty board would drop by 1 multiplier (24 dmg with Mind Shatter). In that case I would choose to drop Prophet Velen, since he simply costs more (dust and mana) as well as limit you to running only 1 copy. It does make the Greater Diamond Spellstone more reliable, but also lowers your potential with Holy Smite combos. In that case, I would add double Loot Hoarder and remove a Mass Dispel in the process.

PS: If you replace Bloodmage Thalnos and Prophet Velen as mentioned, insuring the eventual Loot Hoarder resurrects, you also save yourself 3200 dust in the progress. Making this deck cost 4000ish dust in total, making it a budget version with a very small OTK potential (would require a Clockwork Automaton on board before you pull off your combo to reach 4 multipliers.)