Hearthpwn

Felt like making a deck heavily based on the demon tribe and suprisingly it actually works pretty well. Used it to climb Legend ladder to rank 18# so far. Proof: http://imgur.com/qPdZdSG

How to play ? 

Very simple, just try to curve out and always fight for board. Demonwrath actually is an amazing tool for that purpose. Basically all your minions are unaffected by it so this card allows for huge temposwings.Based on the matchups you face, you have diffrent winconditions. (Jarraxus vs slower decks, vs fast decks just fight for board once you have it,it snowballs very quickly)

Overall this deck contains a lot of synergystic cards and is a blast to play + you play Illidan Stormrage himself, so your opponents better be prepared Kappa

Mulligan:

Always try to find a curve, keeping 4 drops like Voidcaller is only recommanded if you are on the coin. The current meta is pretty fast and tempoish so you need plays every turn ! Just think of what your opponents could play the first 3 turns and how you can counter it the best, overall best mulligan approach with this list.

Cards to consider:

Defender of Argus, Big Game Hunter,Ironbeak Owl,Knife Juggler andAcidic Swamp Ooze are all cards you can probably include and cut cards like Flame Imp or Mistress of Pain depending on what matchups you face the most. The list atm runs no techcards, because techcards always hurt a decks consistency and I felt like most of the time they are not needed, but feel free to experiment yourself!

Dr. Boom is probably better as Illidan Stormrage, so replacing it with Boom is an option. Boom has no synergy with Voidcaller but yeah, Boom is Boom Kappa 

 Some Screenshots from my climb :

1HP Comeback vs Tempomage Kreygasm