So. What started like a meme idea of combining the best Priest shells which are Dragon and Deathrattle turned out to be a pretty good idea. I wasnt expecting a lot from the deck and I've never imagined it to be strong since reactive Control decks are dead in Wild. Well. It seems that if you try to make a Reactive Control deck in the best Control class it still might work and it can have a punch against wide variety of decks.

First thing which is really important is that the deck is fun to play. This screenshot should be pretty good prove

Second thing is that it took me from dumpster meme legend to leaderboard legend so it has some viability at least in Legend ranks

Third thing is that if you have Aggro pocket meta. Then dont play this and play rather something else. However if your meta is flooded with Control and Combo, This is the deck which is at top of that meta food chain.

Mulligan is simple:

Twilight Whelp,Loot Hoarder,Dragon Breeder,Duskbreaker,Power Word:Shield,Dirty Rat are all good picks in your mulligan hand

Now lets talk about the key cards and what makes this deck good

1. The key cards are the one which are one of the best minions that Priest has in the game. Twilight Whelp,Duskbreaker and Drakonid Operative are the reason why Dragons in Priest works. They have strong effects,good stats and single-handedly carry the early game and midgame while still being quite nice in late game. If we look at Deathrattle shell,then things there are interesting as well. We have Voidcaller+Voidlord like package in form of Coffin Crasher and Obsidian Statue but that is not where the synergy ends. Every Deathrattle minion which is included here has a very powerfull deathrattle which makes your Nzoth insane (except Loot Hoarder). That makes your Twilight Call a pretty vertisalle tool and overall ensures that you make a strong powerfull plays which make an impact on board. Finally we have the 3rd shell which is Thief shell. The thief shell here is Archbishop Benedictus which is one of the best Priest legendaries and Murozond which is pretty strong legendary as well. Archbishop Benedictus gives you an edge over matchups like Odd Warrior,Jade Druid or Mill Rogue and Murozond makes sure that you make as powerfull plays as opponent with 8/8 on top(I've had matchups where that fella fully copied opponents Dragonqueen Alextrasza turn or turned me into Deathstalker Rexxar.
2. The second important thing which makes this deck work is how the shells flow from one to another. Yes, the early game and midgame is Dragon heavy but the Dragons are still strong in late game as well thanks to Battlecry cards and Murozond. Yes,the lategame is focused mainly on Deathrattle plays but the Deathrattle synergy pops up earlier thanks to Loot Hoarder and Twilights call as well. And yes,Drakonid Operative is a Dragon same as Murozond is but they are also part of the Thief Priest shell and they are pretty strong minions
3. The dwarfs. The goddamn dwarfs are strong. Dragon Breeder is insanely strong card. Not only does it copy Duskbreakers and Drakonid Operatives in Midgame,it can also copy the Twilight Whelp in early game to help you in board advantage OR copies the Murozond in late game which is pretty strong effect as well. It also synergises well with the strongest dwarf in the game which goes by the name Brann Bronzebeard. You see. Brann really likes to synergise with Dirty Rat to crush your opponents dreams. Brann also has some experience with Dragon breeding so on turn 10 you can go Brann+Drakonid Operative+Dragon Breeder resulting into 2 additional copes of Drakonid Operatives. Believe it or not Brann is also greedy bastard from time to time and combined with Benedictus he ensures that you will never lose from fatique. From all that fighting with League of E.V.I.L. he had gone a little mad and his madness with Duskbreaker rivals the madness of Dr.Boom. Long story short dwarfs are good. And Brann is a madlad.