Hearthpwn

I just took like 4 gul dans and every time ibplay one, you summon 2 as much demons as last time, so i filled my board with 6/6 and killed azari. He did fatigue me but i survived.

Beated easily with priest. I had my minions stealthed and the mega winfury poisonous weapon to remove the biggest demons. Velen helped a lot. So far ithink the hardest boss is king towaggle

I beat him with a hunter deck, but it was kinda lucky as well, i got permanent stealth and 2 fledglings, also i had double health, so he couldnt even dream to finish me before i defeated him, but basically you probably need a face deck to make this bossfight as easy as possible.

Try and play with shaman, 4 or 5 boss is either deathrattle guy or wax guy, 75% lose, wax or deathrattle guy as 7th boss guaranteed lose.

as warrior I got the artifact that makes your weapons cost 1 mana. by the time I got to him, I had 2 1 mana woecleavers, and 5 Y'shaaraj's. Needless to say I won.

Just defeated him with giants warlock and a Scepter of Summoning to get Molten Giants on the cheap; even though he burned half of them. I also got Val'anyr from Portable Forge which actually helped a lot, i'm so happy i defeated this boss as warlock...never playing warlock in this  mode again >:(.

After 60+ runs with shaman, I finally did it, 7 more classes to go...

Beat him first attempt with stealth freeze mage.
He is slow and clears inneficiently using 1 or 2 damage aoes, my deck was not great with board presence but Mirror Entity into Pit Lord helped a lot, without it I'd have lost at least one Ice Block. As of trading I only attacked Mal'Ganis and a Despicable Dreadlord.
To make a deck consistent enough for that you do frost (mostly cheap, aka frost nova) + chaos (mostly cheap) + giants and secrets (aka Ice Block), I tried more chaos + quest oriented decks but they are often too slow and unreliable.
He burned card generation, health gain, 2 Blizzards and one Frost Nova, I think I only used one Cone of Cold as stall and it was more than enough.
Tl;dr: Stealth is OP.

I just beat him with a crappy dragon priest with Justicar's Ring, extra mana crystal artifact, bag of coins and wax rager. I got my wax rager and a soulpriest down on curve to clear his garbage with hero powers. After that it was pretty rough because I didn't have many playable cards somehow. I was forced to play tempo cabal shadow priests and skip a few turns. By turn 8 I got my bag of coins and coined out a sleeping dragon followed by another one on the next turn. Then I somehow had lethal between the wax rager clocking him and the 4 damage hero power every turn. I was honestly very surprised

I won it this way, just filled my deck with as much Jade as possible, so even though if he milled a lot, I still got a big Jade count. My treasures were super helpful as well, had double effect on both deathrattle and battlecry, and the greedy pickaxe got me ramped up really quick

Quote from BigFatMurloc >>

Just means your deck was to slow and greedy

I was able to beat azari with a full blown cthun warlock deck (every single draft I picked cthun buffers, the rest of them sucked) even with summoning an anomolus from the full board of legendaries that he deathed to clear board. But I eventually won when he fatigued himself and I dropped a 35/35 cthun.

most of guys writing here are complete morons, azari is RNG is clearest form (he ate my 3 win conditions, and i could do nothing) and if you dont have luck you have to beat him with 9 heroes

ive already beat him 3 times. 1 with my own facemage, 2 with friends value mage (got lucky with drawing my firelands/aggro start. 3 with jade/tank druid. 4 ayas and 4 jade idols while i had double potion of vitality

so i dont consider him hard. in fact i almost always hope i go against him if im not playing a greedy lategame deck. The only time ive hated playing against him was when i played fatigue rogue. i had the PERFECT fatigue rogue deck with 6 coldlights and 4 gangups but i lost cuz he managed to discard 5 coldlights and 2 gangups and i had no deck left way berfore him :P. Got him down to 10 hp that game tho

But that's Xol lol 

He's a tough boss but one tip I can give is to keep your win conditions in the mulligan.   Several of my great runs have ended because he's milled my wish, c'thun, multiple ayas, etc.  Keeping 10 mana cards in the mulligan isn't crazy against this guy.

He is easy if you build pure jades. He cant mill enough jade cards. 

Quote from Frozen_Inferno_1 >>

His hero power is a 0-mana: destroy 2 cards in your opponent's deck. That is absolutely insanity. I had this really cool spell power priest with Lyra and Velen, etc with a whole lot of stalling spells and I got absolutely destroyed because I was into fatigue before turn 15! This is crazy overpowered and they need to nerf him.