The narrator could be a clue. She does not sound like someone completely neutral.

As
Sylvira Savikas

is likely to show up in the game some things are interesting:
She is an expert on magical puzzle boxes (The gith box) and the outer planes (illithid and forgotten gods connection?)
She lives in Candlekeep so we might revisit the place. A tiefling wizard, infernal contracts, outer planes.
That ties in nicely with some of the speculation here.

The devs also hinted that we would visit another plane and there is a diary entry referring to a strange place that the party seems to get teleported to


Cyric seems to be unable to get involved with much right now. I guess the dead three and some ilithid entity with netherese connections are the most likely candidates right now

I sometimes use thought experiments. I don't necessarily believe in every idea I post for discussion on this forum