Same issue here.
The first time, everybody was moved to the astral plan but Lucian remained behind, in the tomb. Then I killed Bracchus. Then I killed Dallis but she remained unconscious in her dragon form. And the fight is never ending since Lucian is alive... but elsewhere :-)
Sent this one to Larian but no answer at the moment.
Second time, same issue as Beyond : Lucian moved with the rest of the Group. Lucian was killed by Kraken, I killed Bracchus then Dallis in her dragon form. Now I am waiting. Lucian is inconscious with 0 HP, 0 physical armor and 0 magical armor. Dallis is in human form wandering aroud but I can't speak with her. Nothing happens when I sit on the throne.
I guess I am on my way for the third try but I share the super frustrating feeling :-(
