Flawless Master (Layer 12)

Flawless-Master
You need to do all 6 Areas of Torghast of 12 layers
Flawless: Upper Reaches
Flawless: The Soulforges
Flawless: Skoldus Hall
Flawless: Mort'regar
Flawless: Coldheart Interstitia
Flawless: Fracture Chambers
FLAWLESS VICTORY = The Scoring System is what will determine your progression in Torghast, as you will need to reach a minimum score to unlock the next higher layer. Upon defeating the Floor 5 boss in your Torghast run, the Score UI will appear to show how well you performed. And you have to note that Your scores now determine whether you can graduate to the next higher Layer in Torghast. Simply defeating the end boss is no longer enough toadvance. So if you are one of those sly rogues or druids (ie me :P) or hunters who just run to last boss and rush it up is not gonna work .
Here is a breakdoen of how scoring works
Scoring
And remember there are other ways also from where you can increase score (The ones listed in screenshot are the ones he did)
These are the scoring points =
Annihilator =Floor 5 boss killed in under 20 seconds =20
Collector =Collect at least 30 Anima Powers =10
Daredevil =Defeat 2 Elites within 10 seconds of each other =10
Executioner =Floor 5 boss killed in under 40 seconds =10
Highlander =No duplicate Anima Powers =15
Hoarder =Defeat the floor 5 boss with at least 500 Phantasma remaining
(Note: Phantasma required will scale up per member of your party!) =10
Hunter =No elite enemies reached 4 stacks of Unnatural Power =15
Pauper =No epic Anima Powers =10
Pillager =90% of Ashen Phylacteries destroyed =5
Plunderer =Opened treasure chests =5
Reinforced =Collect at least 5 Obleron Armaments of the same type =10
Rescuer =Assisted a denizen of Torghast =10
Robber =Robbed a Broker (Requires Shoplifter blessing active OR usage of a Ravenous Anima Cell)= 5
Savior =All Soul Remnants freed =10
Trapmaster =No trap damage taken = 10
Then there is points for whatever % u cleared the floors 100% = 100 points
Bonus Points gained from actions while Empowered

All of this stuff i brokedown to this specific achievement from Wowhead guide

This is a joke at level 70. Don't be worried. One shot everything. Get an easy mount!

Yep, can confirm, I've done a 16 today and got both 12 and 16 achiev.