Hearthpwn

On my first encounter with this guy, my Horn of Cenarius pulled Deathwing and The Lich King on turn 2. And I had Cloak of Invisibility. Um... yeah.

Had a great Shaman game against him... until he took my Candle. I had absolutely no chance after that.

Don't cast Vanish on this boss. He will not play the chests on the board and his hero power will deal 5 damage every turn.

After breaking 1st chest, KT summoning and endless army of Wax Ragers basically did the trick for me.

EDIT: Oh, and the fact I was playing Priest and could heal KT didn't hurt either ;)

The first turn is big. He has 6 buffs for chests, and will try to use one on his first turn on 3 mana. If he passes you are in good shape. If he puts one buff on a chest, ignore it until it gets a second buff, then kill it, and pray for a good reward. If you are behind on board, all DPS goes on his minions; go face if you are even or ahead (the chests will usually trade with your minions for you...but if you play taunts, the chests will trade into them and die). Lightbomb is the biggest threat, don't overextend. You can't do much about Spirit Lash, he's gonna heal for at least 15 at some point.

Got to admit, I loved this boss. Had the board full of legendaries, and found myself with 8 x 26/26 C'Thun in my hand. With double battlecry. 

I just got the Golden Kobold from the chest he killed himself (a 1/1 copy he made) and got Alexstrasza. Turn 4 GG, as a warrior

Vustrasz the Ancient's hero power is Vindictive Breath. Here's his deck.

1x Wrathion
1x Ysera
2x Azure Drake
2x Blackwing Corruptor
2x Chromatic Dragonkin
2x Cobalt Scalebane
2x Drakonid Operative
2x Hoarding Dragon
2x Holy Nova
2x Lightbomb
2x Looming Presence
2x Power Word: Tentacles
2x Spirit Lash
2x Twilight Whelp
2x Unidentified Elixir
2x Velen's Chosen

His hero power damage increases if you send his chests back to his hand (or shuffle them into one of the decks).

I actually won outcotrolling him as Priest. 

Insane game, wish I had it recorded. I played The Darkness early and tried to not kill the chests. Eventually I had to kill one. What I got was "draw a card, fill your hand with copies". What this got me was a hand full of that 7 mana Priest spellstone, that revives up to three minions after upgrades. With that, I could constatly compete with his board, but my spellstones got less and less and I still was fighting for boardcontrol without killing the chests, which took a lot of resources. Finally, The Darkness awakes. Boom, Lightbomb. Well, shit. However - I had the dungeon run power that activates my battlecries twice - so there were another 3 candles in his deck. Last spellstone resummons a dormant The Darkness. I finally draw my deathknight and Raza, now being able to compete with his board. Still running out of steam, hard fight till the last turns.

No candles to be seen. He draws and draws, no candle. I actually started to think, maybe this is bugged and once The Darkness awakes, it removes all candles. But no. Literally the last 3 cards in his deck were the additional 3 candles - this might be insane RNG, or still is bugged. Anyway, this wakes up The Darkness. Vustrasz already in fatigue for a few turns, no removal for my huge threat. My last card drawn is the treasure that adapts a minion once for every beaten boss. Adapt The Darkess, above 30 attack windfury to finish him off.

Hell, that was satisfying :D

For those that are having trouble with this guy I'll give you some tips.

1) Chests:

His Hero Power punishes you for killing his chests. I've beaten him twice and never destroyed more than 2. You are the one that sets up the timer, given you control when you destroy a chest or not. His Hero Power deals damage to all enemy characters (that means YOU and your minions) based on how many chest are destroyed. He casts this once per turn every turn. 

2) Pace of the game:

Your main aim is to out tempo him. He has spells (buff, card draw) and dragons.  Given he has very little minion space to play with, you should try to get a big guy out there on the field asap. Most of the time you can do this by breaking one chest and obtaning Wondrous Wand. If you managed to do this, the fight becomes a joke. Take into account that he runs Drakonid Operative and he may get a card from your deck (and you better pray he doesn't steal a board clear).

I defeated him with Deathrattle Jade Rogue so it was rather easy. I just played deathrattle jade minions, and they spawned 2 jades (I had double deathrattle effect) so in 4 turns I already had a 7/7 jade and so on. Good luck :)

One thing to note is that it does damage based on how many chests fewer than 5 (or is it 4 he starts with, whatever) he has. This means if he uses anything to copy the chests (the unidentified elixir that summons a 1/1 copy) or if you play Marin the Fox (special voiceline if you do!) then those won't count towards the hero power if you destroy them AND can be used to reduce the damage done by the hero power. I played Marin and his heropower did one less damage next turn.

But yeah, solid explanation. Just hammer him down and if you need a hail mary then you can break a chest. If he somehow copies any of them, you basically get a free treasure.

Ive only seen 3 final bosses but this guy has been the hardest.. and im about to face him right now -_-

Hardest Boss by far.