Some characters are already known, some of them have a high chance to be in BG 3 (this listing therefore makes no claim to completeness):
Thanks for sharing! Yes, of those, Krydle would make sense given the Mindbreaker comic, Bane and the rest of the Dead Three we can assume to be at least part of a subplot given what we find in the ruined temple, Duke Ulder we already know is involved and has been kidnapped and taken to Moonrise Towers, and the two thieves’ guild members could reasonably be people we can meet in Baldur’s Gate when we get there. I understand that Bruenor and the rest of Drizzt’s companions have already been reincarnated in the books (and yes, I also wish that more characters would die and just stay dead to make room for new ones!) so I guess we might see him and the rest of that gang in a cameo as we did in BG2 but I hope no more than that, and could do without even that much.
I agree with you and fylimar that reintroducing old characters can easily be overdone (as happened in BG2 to my mind), and certainly wouldn’t support bringing back any more individuals who have either died or should have died of old age, unless there is already independent lore establishing that they are still present in the 1490s. But I would still enjoy coming across little Easter Eggs that reference characters from the previous games without warping the plot of this one. For example, I liked coming across the book of Faldorn’s teachings in Kagha’s chest, but don’t particularly want to find Faldorn alive and well in Cloakwood if (when?) we get there!
