Do you want this character to come back? Does it cheapen the narrative sacrifice for you?
Sorry, I haven’t played the 5e spelljammer adventure, I don’t really play 5e anymore. But spelljammer would make plane hopping make total sense and fit the narrative.
Obviously I don’t know your game, your table or your players so take everything I say with a grain of salt.
Why is true resurrection out of range but plane hopping isn’t? This seems like a great opportunity to have them complete a quest for some high level NPC who does have access to true resurrection, possibly with motives that run contrary to the PCs? You can have the dead PC run another character for the duration of the side quest.
If they are already half way to the plane where this character’s soul is, bringing the dead PC back to the material plane would revive them as far as I was concerned. Good luck getting them back though, also if it were my table there would be consequences to reviving this way.
Just as a side note it sounds like you are looking for the “correct” answer for what would happen in the forgotten realms, always remember you are the DM, correct can be whatever you want it to be.
Best of luck from a fellow DM! Hope you have a great next session, sounds like you are really invested and your players are lucky to have you.
Depending on your DM, you might also want to take a look at something like OSRIC.
Happy Gaming!
Just for clarity, you are looking for an online reference for D&D 1st Edition?
If that is the case, here is an online reference. I don’t know if it’s better than a PDF though.
In 5E, no. In OSR, yes!
Knock #2 by the merry mushmen has a set of actual d666 tables for generating a pact with a devil.