How it works:

Survive the early game by controlling the board with removal spells and sticky minions/demons, until you summon Highkeeper Ra for the win. In order to do so, Emperor Thaurissan must reduce the cost of SOME of the combo cards. You may sometimes have to assist with additional damage from your minions, or just straight up OTK your opponent with Highkeeper Ra+Drakkari Enchanter for 40 damage. You have to draw as fast as you can, which means tapping your hero power several times. Don't be afraid to Mortal Coil your own Kobold Librarian, because the key here is to assemble all combo pieces to go off. Time is of the essence and disruptive strategies like Dirty Rat, Deathlord and Skulking Geist, can ruin your chances to victory.

To perform the 40 damage OTK combo you need Emperor Thaurissan, Generous Mummy, Treachery, Glinda Crowskin, Mogu Cultist, Dark Pact and Drakkari Enchanter to be available. Let's address some possible scenarios here:

• Have Emperor Thaurissan tick once on Generous Mummy, Treachery, Glinda Crowskin, Mogu Cultist, Drakkari Enchanter. Next turn play Mummy and Treachery on, it to pass Mummy to your opponent (2+2=4 mana). That way cards in your hand cost 1 mana less. You then play Glinda + 6xCultist (4+6x0=4 mana). You sacrifice Glinda to free up space with Dark Pact (0 mana). Then play the last Cultist (0 mana). Highkeeper Ra is summoned (4+4=8 mana) and then you play Drakkari Enchanter (1 mana). End the turn and your opponent's life with the OTK combo. PS: If you don't have one of the cultist or pact in your hand when Emperor ticks, it's fine since Mummy will take care of the cost. The same happens if you don't have up to one of the more expensive cards since the combo needs 4+4+1=9 mana.

• If you don't have one or more of the Mummy, Treachery or Enchanter in hand when you need to go off, you can hit everything for 20 damage: Tick on Glinda, 2xCultist and Pact with Emperor. Next turn play Glinda (5 mana) + Cultist (0 mana)+ 5xCultist (5 mana)+ Pact on Glinda (0 mana)+ last Cultist (0 mana), to summon Ra (10 mana).

• If your opponent has Skulking Geist and destroys your Dark Pacts, there is still hope. You need Emperor to tick once on Mummy, Glinda, 2xTreachery, Drakkari and Cultist (not necessarily). Play Mummy+Treachery (2+2=4 mana), then Glinda+6xCultist (4+6x0=4 mana), then Treachery on Glinda (1mana) and then play the last Cultist (0 mana) to summon Ra. Finally, play Drakkari (1mana) for a total of 4+4+1+1= 10 mana and 40 damage to the face.

• If your opponent has Skulking Geist and destroys your Dark Pacts and you used one copy of Treachery (for the Doomsayer+Treachery combo to clear the board or mess with Big Priest's resurrection pool), you can go for the 20 damage Ra. You will need Emperor, Drakkari, Glinda, Treachery and 2xCultist in hand. Double tick with Emperor+Drakkari. Next turn play Glinda (4 mana)+ 2xCulltist (2x0 mana)+ 4xCultist (4 mana). Treachery on Glinda (1 mana) and play the last Cultist (1 mana), for a total of 10 mana and 20 damage to the face.

Remember to always have an empty board before going for the combo. Note that sticky demons like Voidcaller / Voidlord / Bloodreaver Gul'dan's Battlecry and Zilliax+Antique Healbot should be cleared out of the way for that reason, so plan your moves accordingly. On top of that, you should keep in mind that the opponent must have an open spot for your Mummy. If you use Treachery on Glinda on a full enemy board, it's OK since she will be destroyed.

Replacements:

You can replace one copy of Lesser Amethyst Spellstone or Lord Godfrey (if you don't have him), with an extra copy of Antique Healbot.

With the rise of singleton decks that run Skulking Geist, the last scenario is the reason why I don't substitute one copy of Mogu Cultist for Lesser Amethyst Spellstone or another copy of Hellfire. That being said, I would pretty much keep the deck as it is for now.

Mulligan:

Aggro: Kobold Librarian, Mortal Coil, Doomsayer, Voidcaller, Defile, Hellfire.

Control: Kobold Librarian, Voidcaller, Sense Demons, Emperor Thaurissan.