From BG1 we have the following portable premade PCs available for importing:
Dernel : Halfling Thief
Lessa: Elf Thief
I could imagine a quest where only one of Bhaalspawn blood could continue onto a cave. CHARNAME walks through some doors followed immediately by a cutscene where some other adventurers go through that same exact path.
Eventually CHARNAME finds a precipice with a magic item or a portal. Upon entering the portal, CHARNAME finds themselves in a weird amalgam dimension which seems to be populated with Bhaalspawn that claim to have come from Candlekeep. This new dimension has a central area along with 10 entrances for CHARNAME and the 9 Importable NPCs back to where they came, but the encounters have to be completeable before they'll start working again.
Throughout the confusion, it looks like this amalgam dimension is being attacked, An Irenicus from the Longer Road who went back and destroyed Suldanesselar is coming to hunt the Bhaalspawn from that dimension. Another dimension's Sarevok who never died enters with the full force of their flaming fist army to destroy his dimension's Bhaalspawn. An sullen Gorion arrives with an army of Harpers to correct his mistake of raising his dimension's Bhaalspawn. (Other encounters too).
Eventually companions of other dimensions arrive. A redeemed Irenicus is appalled by his counterpart's inability to overcome his cruel nature. One Bhaalspawn is in an Imoen relationship and another one a Sarevok relationship and other Bhaalspawn are bothered by those incestrous implications. One Bhaalspawn is in a relationship with Khalid in a dimension where Jaheira was killed. Eventually, CHARNAME and his/her counterparts are able to figure out how to reactivate the portals to allow themselves to return to their home dimensions. Some hasty goodbyes are had and CHARNAME and companions return to the entrance of the cave with the portals forever closed.
