Board Thread:The Panopticon/@comment-24894325-20161008100044/@comment-33705047-20181113191401

The way it seems to be is that after regeneration, the previous incarnation separates itself from the current one and becomes “alive” for lack of a better term.

They’re not hallucinations, the Eight actually takes over the Eleven to speak to the Doctor. I guess it’s like; after they die, they go to some form of afterlife in the current incarnation’s head, but have some interaction with the real world.