The Mind-Killer

This is, as has been noted, a reference to the Litany Against Fear from the Dune series of novels. It says, in full:

I must not fear.
Fear is the mind-killer.
Fear is the little-death that brings total obliteration.
I will face my fear.
I will permit it to pass over me and through me.
And when it has gone past I will turn the inner eye to see its path.
Where the fear has gone there will be nothing.
Only I will remain.

This is the hardest achievement of the meta imo (besides the heroic boss grind) because of the very large room for error. The crossbowmen will use Dread Spray several times in a single visit, and the fight can last a good while (10+ minutes).

Each Dread Spray lasts 16 shots, each shot targeting an eighth of the shrine, distributing the shots evenly to the shrine. (Divide the shrine into a pie, each section will be hit twice per dread spray.)
Each crossbowpanda has his own pattern for the 16 shots, which appear to start in the same section every time. It would be hard to describe the patterns in text.
Here's a Picture of the patterns, and a video of them on live.

Since the advent of Legion, I believe this page is in need of an update. I volunteer.
So...
How to Solo at level 110 with 790+ gear level:
1) Unload with everything you've got.
2) Loot.
3) Mic Drop & Exit.