Hearthpwn

You need:

• Prince Keleseth - What can I say?
• Spellbreaker - You need just 1 copy before turn 5 to silence their Possessed Lackey. or to silence the Voidlord or Rin, the First Disciple and push face damage before turn 10.

Situational:

• Harrison Jones - Only keep it with Spellbreaker. If the meta has more Skull of the Man'ari, I may even keep without Spellbreaker in hand.
• Cabal Shadow Priest - Only keep it with coin and without Spellbreaker. This provides a third card in deck to remove Possessed Lackey
• Spiteful Summoner - Only keep it with Spellbreaker. Makes big threat and pushes face damage. 
• Northshire Cleric  - Only keep it with Spellbreaker. Counters Kobold Librarian in early turns.
• Drakonid Operative - Only keep it with Spellbreaker. Strong turn 5 threat that must be dealt with soon. Aim to steal Twisting Nether or Defile to clear the board by N'Zoth, the Corruptor or Bloodreaver Gul'dan. Otherwise Voidlord is a good steal too.
• Medivh, the Guardian - Only keep it with Spellbreaker and Spiteful Summoner. Continue to make big threats and push face damage.

You need:

• Prince Keleseth - This enables superior trade for you vs their minions. 
• Spiteful Summoner - Strongest turn 5 with coin or turn 6 play. You want to play this as soon as possible.
• Drakonid Operative - Strong turn 5 play to steal Spiteful Summoner or Drakonid Operative.

Situational:

• Medivh, the Guardian - Only keep it with Spiteful Summoner. Enables strong tempo play for next 3 turns.
• Harrison Jones - Only keep it with Spiteful Summoner in hand. Occasionally Priest may steal your Medivh or have their own. 
• Stoneskin Basilisk - Only keep it with Spiteful Summoner. A comeback card if the opponent drops Drakonid Operative or Spiteful Summoner before you.

You need:

• Prince Keleseth - What can I say?
• Duskbreaker - Clears 3 health minions they tempo out in first few turns.
• Harrison Jones - Eliminates Secret Mage's win condition Aluneth on turn 5.
• Tar Creeper - Blocks small minions and buys you time into later turns.
• Northshire Cleric - Weakens turn 1 Mana Wyrm and draws a card on turn 2.

Situational:

• Spellbreaker - Only keep it with Duskbreaker. Silences Mana Wyrm if it gets out of control. 
• Stoneskin Basilisk - Only keep it with Duskbreaker. Slows down mage so he cannot drop Kirin Tor Mage on turn 3.
• Kabal Talonpriest - Only keep it with the coin. Prepare to coin out a 3 and follow up with Kabal Talonpriest.

You need:

• Prince Keleseth - What can I say?
• Spiteful Summoner - Strong tempo play to push face damage vs Jade Druid.
• Northshire Cleric - Prevents Jade Druid's early Jade plays such as Jade Idol and Jade Blossom. 
• Stoneskin Basilisk - This slows down Druid's early ramp and buys you time into turn 6 Spiteful Summoner.

Situational:

• Kabal Talonpriest - Only keep it with the coin. Prepare to coin out a 3 and follow up with Kabal Talonpriest.

You need:

• Prince Keleseth - What can I say?
• Duskbreaker - Must keep to clear the initial board on turn 4.
• Tar Creeper - Blocks small minions and buys you time into later turns.
• Northshire Cleric - This removes 1 attack minions and draws a card on turn 2.

Situational:

• Kabal Talonpriest - Only keep it with the coin. Prepare to coin out a 3 and follow up with Kabal Talonpriest.
• Harrison Jones - Only keep it if you have the Duskbreaker and Tar Creeper vs weapon class. 

• Spellbreaker - Should always be included unless Control Warlock vanishes from the meta.
• Harrison Jones - is tech against Mage. There were many secret mages from rank 10-5. The card usually seals the deal on turn 5 if it is triggered. Sometimes Warlock plays Skull of the Man'ari on turn 5 too. Gluttonous Ooze is a good replacement if you do not have the card.
• Stoneskin Basilisk - Serves as removal for big minions vs control and slows down opponent vs tempo. 
• Cabal Shadow Priest - I found that I was not able to consistently draw the Spellbreaker before turn 5, even though I included 2 copies in this deck. This provides a third way to remove the Possessed Lackey without triggering its deathrattle.
• Medivh, the Guardian - This is a win condition vs all control decks, especially control warlock. Control warlock can have up to 2 copies of Twisting Nether and 2 copies of Siphon Soul. It ensures that we are constantly making threats that the opponent has to remove.

• Twilight Acolyte - Stoneskin Basilisk serves the same purpose and does the job better removing big threats. In addition, Twilight Acolyte is not a dragon itself and requires a trigger.
• Psychic Scream - I tested it for a while and felt it was only useful sometimes to remove the full board by Paladin or Warlock. However, I really hated the idea of shuffling cards back to Warlock's deck.
• Dragonfire Potion - Same as Psychic Screen. It's too late to play it vs Aggro decks. And it's not as impactful vs Priests as they have all the dragons.
• Ysera - Even though the deck cuts 2 x Netherspite Historian. Dragon synergy still can be reliably triggered. It does not need another Dragon in the deck. Medivh already provides the late game value and it does not need any more value from Ysera
• Curious Glimmerroot - This card is not impactful on turn 3. I would rather play Tar Creeper to stop the aggression on turn 3. The card draw may steal you a Drakonid Operative sometimes. However, the extra value is not needed in this deck.
• Grand Archivist - It lacks the consistency that I desire. Often when I want to Mind Control a Voidlord, it casts a Free From Amber instead. It occasionally wastes the FFA by picking an inferior minion like C'Thun or Bonemare. After it's played, Spiteful Summoner becomes weaker as there may be no more spells left in the deck.

• Harrison Jones - Gluttonous Ooze or Corrosive Sludge. 
• Medivh, the Guardian - This card's effect is unique and substituting it will decrease the power level of the deck quite a bit. However, if you have to, you can replace it with Grand Archivist, The Lich King, Ysera or Bonemare.
• Prince Keleseth - Hmm. Not really.

Warlock is usually Control lock, Cubelock or Zoolock. Similar Strategies are adopted against the first two. Given many mid-size taunts and 2 x Duskbreaker in the deck, Zoolock is easy to deal with so I will not cover here.

You have two chances of beating a Control lock. The first is during the midgame as you continue to make big threats from turn 5/6 to turn 9. Do not overextend the board as they are likely to have Defile, Hellfire and Twisting Nether. Silence the Possessed Lackey at all costs. If they have a Voidlord out, try to kill it ASAP to prevent it being copied or cubed.  Your primary goal here is to prevent them from summoning and killing Voidlord and push as much face damage as possible.  

Approaching turn 10, Control lock may resurrect the Voidlord with N'Zoth, the Corruptor and Bloodreaver Gul'dan. Save your 2 Mind Control and take their Voidlord as soon as they are resurrected. Save your Duskbreaker to clear full board of Voidwalker. Steal one or two Twisting Nether to assist your board clears.  Exhaust their removals by putting one big threat on the board each time. Your primary goal here to hold on until they run out of cards. 

Priest has many variants. Spiteful Priest and Dragon Control Priest are most popular. Traditionally whoever gets Spiteful Summoner first with good RNG wins the match in the mirror. However, due to the inclusion of Stoneskin Basilisk, you have a chance to neutralize their big minion and come back even if you do not draw your Spiteful Summoner early. With additional value from Medivh, you are heavily favored in this matchup. 

Some Priests run OTK combos. Just focus on clearing their board every turn to stop them making big minions. Be mindful dropping high health minions unless you have taunts in the way. It should be easy to deal with as you have much more value than them.

Secret mage is the mainstream. They typically have some ways of cheating tempo and playing secrets. It's a easy matchup as long as you have a good Duskbreaker clear. You also have multiple taunts to stop their aggression if you did not draw the Duskbreaker. Save the Harrison Jones on mulligan for the Aluneth. You wins the game by exhausting all their cards in hand.

This is a tough matchup vs either Murlock Paladin or Dude Paladin. You should have a chance if they do not have an insane start. Duskbreaker and taunts are main ways to stop their aggression. Attempt to clear the board always until they run out of steam. You win by building a big board. 

Pro tips:

• Prefer to drop multiple minions over a single big minion. Buff the taunts to force them trade multiple minions into it.
• Save your Harrison Jones for Vinecleaver.
• Take their Righteous Protector with your Cabal Shadow Priest to avoid double trading into it.
• They normally do not have Equality or Consecration. So it is safe for you to extend.
• Paladin has Divine Favors to reload so you actually do not want to discover a card from Drakonid Operative. 

If you still have a hard time with Paladins, Replaced 2x Stoneskin Basilisk with 2x Lone Champion. In this case I will intentionally not play Northshire Cleric on turn 1 with Lone Champion in hand. 

Jade Druid is fairly weak in first few turns. Try to slow down their ramp with Stoneskin Basilisk. Once you have a good Spiteful Summoner or Medivh turn, pushes as much face damage as you can. You can close out pretty fast without the aid from Skulking Geist.

Miracle Rogue can cheat tempo in first few turns. Again Tar Creeper and Duskbreaker are your best friends. Once you survive and stabilize, it should be smooth sailing from there.

vs Kingsbane Rogue, you need control the early game and avoid trading at all. Once they buffed the blade up to 5+ attack with life leech, it's difficult to rush them down.  

The only viable archetype is Spell Hunter. Save the Duskbreaker for the Lesser Emerald Spellstone. Feel free to extend the board as they have a hard time clearing multiple minions.

I've seem mostly Jade evolve Shaman. Make good trades and prevent them from having a good evolve. It should be easy matchup for you.

Is this a class? Maybe in the secret cow level?

There are usually mini meta pockets within the ranks. The meta is vastly different within the pocket. Tech and react quickly within the pocket secures a consistently high win rate for you. In general, from rank 5 to rank 4 there is usually a meta pocket. And another meta pocket occurs from rank 1 to legend. Swapping 1-2 tech cards in your deck often drastically changes your win rate against a certain class.

Understand that our deck is primarily targeting Warlock and Priest. It's a greedy control deck that outvalues everything else. Its only weakness is the early game as we sacrifice the 2 drops. We do not have a lot of removals in the deck due to big spells. If the meta consists of fast decks, we can counter them with more mid-size taunt or tempo swing on turn 3 or turn 4. With only 2 board clears in the deck,  try to save it for a bigger clear unless you have to. It's usually preferred to play taunts to delay their aggression rather than the Duskbreaker at first chance. 

For example, if you enter a meta pocket flooded with Paladins, try to cut 2x Stoneskin Basilisk and add 2x Lone Champion. It takes several hits to take down the Lone Champion on turn 3 and it can serve as a mini-board clear. Other taunts or temp swings such as Saronite Chain Gang can be considered as well if the meta is even faster. 

The tech cards slots are Stoneskin Basilisk, Harrison Jones, Spellbreaker, and Cabal Shadow Priest. Read the meta and swap cards in/out accordingly ensures you a fast climb experience. 

Sometimes meta can become extremely hostile. I ran into 8 Dude/Murloc Paladins in a row when playing this deck at rank 1. I lost to all of them and my rank dropped to rank 3. Rather than tech more against Paladins, I picked Murloc Paladin to counter the Dude Paladin in the meta. With another win streak, I quickly got back to rank 1. Then the meta is hostile to Paladin again and I swapped back to this Keleseth Priest deck which got me to legend eventually.

Playing a control deck requires a lot of skills allocating your resources. It is not as easy to pilot as an aggro deck. Have some patience and good luck with your legend climb! 

Here are some of my observations:

• Secret mage dropped in popularity significantly. So I cut Harrison Jones for Saronite Chain Gang. Sometimes when I needed weapon destruction again, I included Gluttonous Ooze instead.
• To my surprise, I did not encounter a lot of Paladins in the last few days of ladder. Maybe people focused less on ladder climbing but more on fun in legend ranks.
• Kingsbane Rogue was much more prevalent than in non-legend ranks, though it was still not mainstream. I started to mulligan very aggressively against them for better results.
• At one point I replaced 2x Stoneskin Basilisk with 2x Lone Champion or 2x Saronite Chain Gang. Think Lone Champion is better vs Murlocdin and Saronite Chain Gang is better vs Dudedin.
• In the end I put back Stoneskin Basilisk in the deck as it was quite powerful in a lot of matchups. I ended up swapping Spellbreaker with defensive cards depending on Paladin/Warlock population.