Just a thought, but I sometimes wonder if it's not the fabled Gith inside the box.
Vlaakith only rules because Gith disappeared after going to make a deal with Tiamat. Is it possible that the lich queen has had the true githyanki leader imprisoned in the box the whole time?
Again, I think of the tablet on the illithid ship: "Images flash through your mind. A brain. A githyanki warrior. And centuries of darkness."
Is the warrior in question Gith? Are the centuries of darkness talking about being imprisoned within the box?
Ooh! I don’t know, but that’s another really fun idea to ponder on.
Kinda doubt because if it is in fact an Infernal Puzzle Box, then the box doesn't work like a Tardis (Bigger on the inside, Doctor Who), and originates from the Nine Hells. They're used to safeguard diabolical contracts between a devil and a mortal. Look up its full description if you'd like some material to enjoy speculating on. I find the more interesting question to be why does Shadowheart have it, seemingly prior to ending up on the Nautiloid? Suggests she's been to the Nine Hells before or directly/indirectly received/stolen it from someone who was.
Check
this little nugget and its comments for some more speculative food for thought ☺️
