During the Final Chapter of the Campaign, it seems like Xal'atath has some unique whispers to Shadow Priest players, showing that their knaifu hasn't forgotten them.
Looking through the community and datamining, there seem to be four different interactions. The interactions depend on what you did with your Priest in the past. The interactions happen as the player is close to the end of the Chapter 5 Scenario.
The criteria is about if the character has the Legion artifact questline done and if they cleansed or not the Eye of N'zoth from BFA.
Many Shadow Priests wondered if there would be any special interactions with their former artifact. This raises hope for further interactions and maybe story choices.