So during this preview we learn a lot about how Bastion as an afterlife operates.
When a soul is sent there it loses it’s form.
That form is then reshaped into a Kyrian.
The memories of the old soul are torn out. Family, friends, enemies, trauma. Everything that made them who they are is forgotten.
They become a fully fledged Kyrian, their old mind and body gone forever. The Kyrians basically destroy the souls and identities of mortals in order to reproduce.
Case in point, we see a Tauren who has 'ascended' to become a Blue Human.
We then 'help' him by banishing the memories of his comrades in arms, friends and family. Essentially turning him into a blank slate, destroying all that he was and condemning him to an afterlife as somebody he isn't.
Now this would make a fascinating dystopian afterlife. But that's not how it's portrayed. This is portrayed in an entirely positive light and the player is -forced- to help the Kyrians defile the souls of those unfortunate enough to be sent to Bastion. The Kyrians even admit that they'd do the same to the player if their physical form wasn't keeping them tethered to who they really are, and the player character just seems to be fine with that?
This is during the leveling experience, so it's not even covenant-exclusive stuff.
What the fuck Blizzard?
EDIT: New info
https://wow.gamepedia.com/Step_Back_...dge,_My_Friend
Talking to Eridia
Such an intensive cleansing may require your martial expertise.
Are you prepared to aid me?
Gossip Yes, Eridia.
Eridia says: Hold this burden in your mind, Acolytte, so the Vesper may cleanse it.
Acolyte Nikolon says: I can see her... must I let her go?
Five Nikolon's Uncertainties appear.
Eridia says: For eons we hve cultivated the Aspirants in our care. Trust in the process.
Acolyte Nikolon says: Her memory is a gift! It will allow me to serve you better!
Three Nikolon's Distrusts appear.
Eridia says: You will see her face in those you must serve. Let her go, Acolyte.
Acolyte Nikolon says: There must be another way!
Two Nikolon's Doubts appear.
Eridia says: She is still to near to you. In time, we can try again.
Acolyte Nikolon says: There will never be enough time. Never!
Nikolon's Dispair appears.
Acolyte Nikolon says: I will... not... let you... take her! Not ever!
Eridia says: Acolyte! No!
Acolyte Nikolon becomes Fallen Acolyte Nikolon.
Talking to Fallen Acolyte Nikolon
<The Acolyte breathes heavily.>
This is... I am...
Gossip Are you well?
Fallen Acolyte Nikolon says: If this is truly the only way, then I will find another.
Fallen Acolyte Nikolon says: You will cast me out for this. I have seen it before.
Eridia says: You are beyond our aid, now. You must leave the temple. Go before you are seen.
Fallen Acolyte Nikolon says: Know this, Eridia. I am not alone.