Hearthpwn

Mortal Coil - Standard 1 mana Warlock removal that cycles.

Power Overwhelming - Gives you a bigger target to Shadowflame or just to trade up to help stabalize the board

Dark Peddler - Excellent 2 drop to fish for Mortal Coils, POs, Voidwalkers or side stuff like a Shifter Zerus, Abusive Sergeant or Sir Finley Mrrgglton.

Demonwrath - Since this is Renolock we can only run one-ofs for board clears. This is the next best thing to a second Hellfire, and it's sometimes better like when it's played against a Paladin, or Shaman.

Imp Gang Boss - Amazing 3 drop. Typically generates 4/4 of value and trades amazingly into aggro decks.

Spreading Madness - I've been testing running Spreading Madness over Shadow Bolt and found I like it a lot more. Yes there is the chance it pings you but against aggro boards it's very likely to ping their small minions and act as a pseudo board clear. Also, Reno can heal off any damage it does to you.

Hellfire - Awesome board clear. Kills Grim Patrons, mummies from Mirror of Doom and any aggro board.

Shadowflame - Has strong synergies with Power Overwhelming. Your secondary board clear. Can be used lategame on Infernals to kill bigger boards.

Usher of Souls - This is a C'Thun deck, here's some C'Thun synergy. You'll be trading alot to survive and this has nice vanilla Pit Fighter stats.

Siphon Soul - Standard hard removal spell. Save it for big enemy minions in a control matchup. In an aggro matchup it's probably a dead card, but if you can fit in the mana to cast it the heal is nice.

Twisting Nether - Continuing with the theme of running a lot of board clears we saved the best for last. Your opponent evolved a Twin Emperor Vek'lor into Tirion Fordring and Ragnaros the Firelord? Wipe the slate clean. This is much better than DOOM! because it's cheaper.

Lord Jaraxxus - I shouldn't have to explain why Jaraxxus is so good. Instawins control matchup. Can heal you in clutch situations. Weapon gives tons of removal. Hero power swarms board with lategame threats.

Beckoner of Evil - C'Thun synergy River Crocolisk. Moving on.

Brann Bronzebeard - Where to begin. This card has so many synergies with other cards in the deck it's incredible. Double healing with Cult Apothecary, double C'Thun, double any of the battlecry C'Thun buffs, double Twilight Drake, double Cyclopes, etc. The list goes on and on. Also has a solid statline to trade with an aggro board. Overall awesome 3 drop.

Disciple of C'Thun - Better version of Ironforge Rifleman. Does an extra damage in exchange for 1 less health, which is super worth it and also has C'Thun synergy.

Mind Control Tech - Solid against aggro boards early because it gives a 3/3 body + an enemy minion and it removes that minion from their side of the board. Stealing Knife Jugglers or Darkshire Councilman can be game-winning.

Twilight Elder - C'Thun synergy Spider Tank. Moving on.

C'Thun's Chosen - Similar to Piloted Shredder but with C'Thun synergy. Really good.

Cyclopian Horror - This card is interesting. Has Brann synergy and against a board of 2 enemy minions is equivalent to a Sen'jin Shieldmasta. However, against a huge zoo board this card becomes a godsend. Really worthwhile.

Defender of Argus - Solid upgraded version of Sunfury Protector. Gives you some stronger midgame taunt walls to stave of aggro damage.

Spellbreaker - Better alternative to Ironbeak Owl to supply the deck with a silence effect.

Twilight Drake - Solid 4 drop if your hand is full from life-tapping.

Crazed Worshipper - New taunt alternative to Sludge Belcher. Has C'Thun synergy.

Cult Apothecary - New healing alternative to Antique Healbot. Heals for the same amount against an aggro board of 4 and can heal for potentially more.

Emperor Thaurissan - Discounts your hand. Has higher value the more cards in your hand. This is Handlock. He's pretty great.

Reno Jackson - Pretty useless. I don't know why he's in the deck. Not important at all. Would recommend replacing him with Magma Rager if you have enough dust to craft it.

Sylvanas Windrunner - Excellent 6 drop. Similar to MCT, if it can steal a card it automatically gets it's value. Even playing it on an empty board forces your opponent to answer it or risk you stealing his big drops. Awesome counter to an opponent's C'Thun.

The Black Knight - With all the huge taunt minions that are crawling out of the woodwork and the need for premium removal that isn't really understatted (i.e. Big Game Hunter) TBK fills the niche.

Twin Emperor Vek'lor - I don't know what to say. This card is incredible. You defenitly will have C'Thun to at least 10/10 by the time you play this guy. So he's two 5 mana Druid of the Claw bear forms, for only 7 mana. Played on curve he is a monster. He curves out just as aggro has their final push for the win.

C'Thun - This card is bonkers. It's pretty much an instant win button. Clear the enemy's board, deal a lot of face damage and summon a huge monster that they need single target removal to get rid of. 

That's the decklist. If I get over 100 likes I'll include a mulligan guide.