... though I wouldn't expect too much a novella dealing with the Afterlife in general.

The first idea that came to my mind is that the novella might tell the story of the "ghostly procession" (those ghosts were spectral, not mistakable with living people like the other ghosts, and this was pointed out) that was seen beyond the wall of Bandar Eban in TGS, and which Nynaeve/Cadsuane/Corele went to watch one night. That chapter was called "River of Shadow" There were some "hooks" in that scene (all we know is that funeral procession, a sea of ghosts carrying a coffin, appeared after Rand's arrival in the city... but perhaps we just have to understand since he touched the TP and in his darkness he gave rise to that phenomenon, as he spoiled the food. My thoughts as I read that scene the first time was that these specters had not rose because of the DO like the other ghosts, but were a vision of Afterlife itself, the dead there mourning Rand's figurative death as he embraced Shai'tan himself, the death of the one supposed to release them from the DO's clutches... Yeah, yeah, I'm pretty sure we'll find out the DO is doing something to the Afterlife... my guess is that the "weakness in the pattern" is the Afterworld, the part of Creation thatt needs to touch the Dark One so death is possible within creation, and the Bore goes right through it).

The other reason to believe this will one way or another have to do with the Afterlife is the fairly transparent reference to mythological afterworlds, the river Styx notably.

Btw, it's confirmed that the novella is built around (a) deleted scene(s) Brandon cut from AMOL for pacing reasons.