Hearthpwn

Why no Lyra? You run 14 spells.

I would definitely cut Skulking Geist for a second Bonemare. Bonemare is ridiculously strong - it's one of the reasons tempo decks are good in the current meta, it can convert even a slight board advantage into a big burst of tempo that helps you close out the game just in time to keep control decks from stabilizing and overwhelming you with big threats. Geist really isn't very good in tempo decks, even against Jade Druid - by the time they can start going infinite with Jade Idol, you've already lost. You need to out-tempo them and kill them before that point, and playing a 4/6 for 6 really doesn't help you do that.

Shadowblade is just bad. Vanish doesn't fit this deck at all - your entire deck is built around staying on the board while keeping your opponent off of it, so if you're in a position where you want to Vanish on turn 6 or later, you're way behind and Vanish won't be enough to let you catch up. 

How awful at Hearthstone do you have to be to think Jade Druid is bad at contesting the board? o0

Why so many one offs?

It's super clunky and situational, but I think it's worth mentioning that the Treachery combo is a hard counter to combo decks like Quest Mage. Play this combo lategame when you can set up several pings, force your opponent to discard combo pieces, gg. If Quest Mage or other combo decks become a huge part of the meta, this might actually be relevant.

Shifting Shade, but tbh if you don't have Summoners I wouldn't run the Barnes/Mirage Caller variant.

It's a common, and a staple in pretty much every aggro deck... Just craft them. And for the love of God, don't run a 9-drop in this deck.

This is not an easy deck to play. If you're not willing to invest some time into learning how to survive in various matchups and with various draws, don't bother playing it - you'll just wind up being one of the noobs who posts about how you're losing matches in rank 20 and being downvoted by people who play the deck properly.

It's also not a Tier 1 deck by any means. If your sole priority is maximizing your winrate, just play Cancer Shaman like everyone else. With skilled play, this deck can get you to Legendary and compete there, but you can get there easier with other decks. This is a fun and novel deck for people who enjoy playing unusual Control Priest variants. 

Medivh is essential for this deck. If you don't have it, you shouldn't play this archetype. 

@bromeatmeco: For most decks that run Thalnos, your advice would be correct, but for this deck, early spell damage is absolutely essential. Geomancer is much, much worse than Thalnos, since it doesn't cycle on death, but you really can't afford to run a card without spell damage in Thalnos' slot, so Geomancer is the best of a bunch of bad options. Spell damage is what makes Spirit Claws and Maelstrom Portal playable, and those cards are a huge part of your early game with this deck. 

Bloodlust is a lategame finisher that only works if you control the board. Cutting Thalnos significantly reduces your ability to control the board. This deck doesn't want to run 2x Bloodlust, and cutting Thalnos makes running a second Bloodlust even less viable. Tuskarr is just bad post-nerf, you can't rely on it giving you spell damage and if it rolls any other totem it probably puts you behind even when played on curve.

I'm a little skeptical about running 9 spell synergy minions and only 9 spells to activate them. I would consider cutting at least 1 or 2 C'Thun buff minions (Twilight Elder can definitely go, no real sytnergy with the rest of the deck, and maybe 1 or both Beckoners since it's just not a very good card in general? With more spells, we will get more value out of our Cult Sorc, and all the usual tempo mage spell synergy stuff) for moar spells (which ones is highly meta dependent - arcane missiles, forgotten torch, mirror entity, polymorph - all reasonable considerations. If you see a loooot of aggro decks with small minions, arcane explosion could even have a spot in the deck - we *do* have 3 spell damage minions, 2 of which are 2 drops we want to play on curve...).

Oh, and I'm kinda on the fence about including Edwin VanCleef when you only run one Backstab, three total 1-drops, and no Preparation. You have almost no ability to combo him early game, and not enough card draw to have a great chance of having the cards in hand to combo him lategame (especially since you also don't run Tomb Pillager). Sorry for the double-post; for some reason hearthpwn won't let me edit.

I'm not so sure about Journey Below... I've even toyed with cutting it from my Raptor Rogue deck, since there are so many mediocre-to-bad deathrattle minions in Standard and so few truly good ones that I find myself picking between 3 bad cards more often than I can stomach. And this list doesn't even include Raptor!

One thing I am quite sure about: this deck reaaaaaaaaally needs to include Brann! You run *thirteen* battlecry minions, every single one of which combos well with Brann (Brann + Blade doesn't kill two things, but it double-buffs your C'Thun based on the one thing it kills).

I also really don't care for Beckoner of Evil. I think you can afford to run a greedier mana curve and replace it with C'Thun's Chosen, which IMO is a significantly better card. A 2/3 for 2 is something you only play if it has valuable card text. A 4/2 Divine Shield for 4 is actually worth playing on curve just for the body.

Why do you think Sap doesn't work in this deck? It's not really dependent on synergies/combos with the rest of your deck - it's just a really good tempo card in the current meta. Are you not facing many Shamans? It feels almost mandatory to me in any Rogue deck with so many Shamans running that 6-drop 7/7.

I'd go further than that - it's probably the single best card in the set, period, maybe in the entire game. It's hard to overstate how ridiculous 8/12 worth of taunted stats for 7 mana and 1 card is. I'd say that in the decks that can run it (C'Thun decks), it's better than Dr. Boom - 8/12 is better than 9/9, taunt makes that health-oriented stat distribution even stronger, spot removal only takes out 4/6 of those stats instead of 7/7, and the bomb deathrattle is so RNG-driven that it doesn't consistently add much value to the card (it can even wind up hurting you against Patron Warrior, or any deck that runs Acolytes for that matter). 

Twin Emperor doesn't really have a replacement- IMO he's the main reason C'Thun decks are so powerful in the first place, more so than any of the 10 attack class cards or even C'Thun himself.  You can sub in pretty much any of the usual good lategame minions for control decks, since there's nothing worth running that fills the same role. If you play C'Thun decks with any regularity, your absolute top priority should be crafting Twin Emperor ASAP - he's one of the best cards in the game and this deck benefits more from him than most (since you really really want efficient ways to avoid taking damage, and 8/12 stats worth of taunt for 7 is absolutely ridiculous - but not as ridiculous as the 12/18 stats worth of taunt if you manage to pull off the dream and play him with Brann on the board! All aboard the win train, next stop: value town!)

Malkorak is a weird tech choice that is specific to this list, most C'Thun Warrior lists don't run him and I don't think he's nearly as good as Sylvanas. I would sub in Sylvanas and probably try and make room for a second Brawl since that combo is absolutely devastating in control v control matchups.