Hearthpwn

Not a combo that stands out when you first think of the card, but Tainted Zealot + Defile will usually result in 6-8 damage to the entire board, if theres at least 1 other minion with 2 or less hp left.

I realise that many people in the comment section struggle against "dedicated control decks". The only deck that have AOE that can remove your board is Warlock (and mage with frost nova + doomsayer), so renolock (and freeze mage) should be your only real difficulty.

Warriors will Brawl, and Shamans will Devolve.

Moreover, there are a lot of starting hands than can work without a dragon (northshire, 1/4 wyrmrest agent + kabal talonpriest, ...).

I think this is a bit of a stretch, a 1/4 without taunt on turn 2 is not a good play, and will get you stompted by Pirates or rekt by shamans' earlygame.

Still I think you've got a fine deck and again congratz for hitting Legend.

I would argue that 1 big endgame dragon (Ysera, Deathwing, Chromaggus, Malygos only if you run 2 Holy Nova, Onyxia, Nefarian, take your pick) and 1 utility dragon(Book Wyrm or Azure Drake). 

And to take out probably the Blackwing Technicians, because its not really that good of a card when compared to Kabal Talonpriest.

If you're intent on keeping Velen's Chosen, then instead of a utility dragon I would take Dragonkin Sorcerer which has good synergy with it and Power Word: Shield. Only one though because there are enough 4-drops already.

I like to think of this card as a "Build-your-own Grim Patron."

That's a harsh way to look at it. Medivh, the Guardian is exactly the same as Sindy. No instant impact, big late game card, massive value over time.

Whether Sindragosa can compete with Medivh is a good question, I guess we'll wait and see. 

I have to say I like the deck but I have some critique after playing around with it.

First, 9 dragons. Not enough, not with two Twilight Whelps, two Wyrmrest Agents, and two Blackwing Technicians. This deck's early game critically depends on having a dragon, and 9 dragons means (ROUGHLY, don't kill me staticians) a 76% chance to draw one in your opening hand, without accounting for mulligan - which is by the way another problem, your only cheap dragon requires another dragon to be activated, which means you need to either actively mulligan away your early game to be able to get a dragon to activate your early game, or you have to keep a dead 1-drop in hand. anyhow, this 1 out of 4 games where you wont draw a dragon is a game where you're at a massive disadvantage.

Second, the deck is stretching itself a bit thin. Youve not got the endgame to compete with a dedicated control deck, because you'll get out valued, but you also don't go all-in on the early game cards to beat aggro. With only 1 Potion of Madness, and only 1 Holy Nova, you're really not going to consistently be able to stop pirate warriors or midrange paladins from snowballing. Also with only 1 Dragonfire Potion, a Conceal'ed Gadgetzan Auctioneer is likely to be surviving a turn, and with no real powerful draw you're not promised to get your one-of removals at all.

So those are the two main problems I think the deck has, my suggestions are

1. Add more Dragons, I think 11 is a safer number. - Either Kabal Talonpriest or Blackwing Technician could be cut, having both and fewer dragons is really greedy. They are powerful minions, but they're clipping eachothers' strength.
2. Focus your spells on fighting a specific type of enemy decks. With Netherspite Historian & Drakonid Operative you've got at least limited staying power vs. Control, so I would focus spells vs. Midrange and Aggresive decks, my suggestion here is to add a second Holy Nova, due to its power with Northshire Cleric and the synergy with a deck that likes to have big-health minions on the board makes a healing spell more useful. Velen's Chosen seems redundent in a deck that already relies on high-stat minions, it is my opinion that Velen's Chosen is one of the most powerful cards in the game, but you only run 1, and I understand why - it doesn't mesh well with the deck, so I think it would be best to remove it and make room for a second Nova. 

That's about it. I really liked the deck, congratz on hitting Legend!

Yes, I can't agree more. I've played a few extra arenas since posting my last comment and I must say my opinion of this card is only improving with each time I play it. There are SO many good taunts in the game right now. Hot Spring Guardian, Sunkeeper Tarim(which basically turns the defender into a hard removal aslong as you have stuff onboard.), and The Curator which, even if you didn't pay attention to beasts/dragons while drafting, will pretty much always draw atleast a Beast and sometimes a Murloc/Dragon. This is an awesome sleeper card.

Edit : Also the fact it can go infinite on itself, this card is glorious.

Is it just me or does he say.... "Yo N..." when he enters?

This card deserves a lot more attention that it was given. Most streamers just went "won't be played" and moved on. That is true, this probably won't see play in constructed, but this little guy is a real threat in Arena. Especially for Warlocks and Warriors. Because he can discover (and of course, is 4x times as likely to) your class cards Tar Lurker and Tar Lord. Both of these cards are Arena mvps as they are over statted for their costs and quite difficult to deal with. It can also find Tar Creeper which shares that quality. I rate it a high priority pick in Arena as Warlock or Warrior and an average quality card in arena as other classes.

Quote from FranckN >>

What about lorewalker cho?

I have not considered it. Maybe I should, lol.

Quote from EverBrawl >>

Well, if you go first far more devastating would be Kabal Lackey to Counterspell the opponent's quest, since you disrupt his main win condition considering his deck is built around quest completion. Stealing it gives you miserable benefit if any given at all since you can only complete the priest quest easily. You must be extremely lucky to pull the druid quest if you res Chillmaw with [card]N'Zoth, the Corruptor[/card] AND discover another 5 attack minion via Kabal Courier. You can't play 7 taunts (warrior) and you have total of 7 one cost minions (hunter) so this would be pretty hard to do, you don't have 6 buffs (paladin), You can't discard even a single card (warlock), rogue quest can be theoretically  completed if you manic soulcaster a minion you already run 2 copies of and discover a 4th with courier which is nearly impossible, you don't run any murlocs (shaman). 

So, the question is WHY do you want to steal anyone's quest?

*edit: about rogue quest - didn't notice you run echo and duplicate, which makes it lot easier to complete

The deck started out with the idea of countering the enemy quest. Then I just ran with it because just playing Secret Mage is boring.

I don't know if stealing enemy quests is possible, but this is this deck's point. Could have some fun disrupting early-Un'goro meta. I'm personally thrilled to try.... could use a lot of polishing though, and I would love for some feedback.

Here it is : 

Any and all feedback is really appreciated. If quests are not hard-coded to be unstealable, I really want to make this deck work. My #1 consideration right now is cutting some one-drops. I'm not quite sure yet, this is my first time theorycrafting a deck. I can't really test it out.

I'm confident the deck could win games without the gimmick of stealing quests though, which is an important thing if the deck is going to work.

The Black Knight: "Delicous, with a hint of dinosaur bone."

Basically every card that costs 7 or more is a viable finisher in arena just because there are not that many.

well if you discarded Deathwing before, then you coin this out t5, then the enemy kills it. I guess turn 5 and a half.