What the achievement asks
Complete every objective in the Horrific Vision of Orgrimmar, in a single visit, with all five Faceless Masks active. Fifteen points.
This one is not tied to your account. It has to be done by the character that runs it.
Five masks is the maximum difficulty, every objective means the lost areas as well, and a single visit means there is no coming back to finish.
The Valley of Spirits will not complete if you are too strong
This is the single most important thing to know about this achievement today, and it has nothing to do with difficulty.
If you kill the final boss of the Valley of Spirits in one hit, the objective does not register. The zone stays incomplete, the vision cannot be finished, and nothing tells you why. It has been reported continuously from 2024 to the present.
The reason is that the objective is tied to the boss casting Hopelessness, and a boss that dies instantly never casts it.
Hit him weakly and wait. Unequip your weapon if you have to, avoid damage over time effects, and let him begin casting Hopelessness. Once the cast has started, he can be killed and the objective completes.
Players who did four full visions without ever completing the Valley of Spirits were hitting exactly this.
Prepare before attempting it
Two things decide whether a five-mask run is possible, and neither is skill.
A full Titanic Research Archive. Every talent at every rank. Solo clears have been done a talent short, but not many.
Cloak rank. Unwavering Resolve takes it to fifteen, and cloak rank is the sanity you have to spend. A full clear has been reported at rank 12 by a class with strong solo tools, but that is the floor rather than the plan.
Skip what you do not need
Once the Archive is bought, mementos stop mattering, and that changes how the run should be played. Chests and packs that are not required become pure sanity cost.
Take the shortest line between objectives. Anything that lets you avoid a fight entirely is worth more than the loot in it.
Its counterpart
The Most Horrific Vision of Stormwind is the same achievement in the other city, and both are needed for the category.