If a character dies whilst mind-controlled, what effect (if any) does this have on their spirit after death? Shades have a tendency to relive the days / hours before their death, so it feels like they might be susceptible to having the effect of the mind control continue beyond the point it "should" do. Ghosts also usually have difficulty "changing" - but does having an external effect on your behaviour wear off really count as changing in this case?
I'm thinking of a few different scenarios:
Whilst within the original duration of the effect
Once the original duration has worn off
Contacting the Spirit via Whispers Through the Black Gate
It is not necessarily the case that a ghost always is the spirit of the deceased person. It is a spirit, but perhaps not the same one. So, if a mind-controlled person dies, and the circumstances are of the sort that might give rise to a ghost, there is more than one possibility, including some not listed:
The ghost permanently acts as though it were mind-controlled, because the spirit naturally has this behavior, since it is emulating the behavior of the person in the hours before its death.
The ghost does not act as though it were mind-controlled, because it was never mind controlled.
The ghost exaggerates aspects of the behavior so that it is more obvious that it was controlled.
IMC, it sounds like a perfect way to flag an NPC as a terrible person, and so I'm happy to let people do it to other people. We say Ars is a game of consequences, and sometimes the consequence is that you really hurt people in an unfixable way, and then take a sort of some solace from the idea that ghosts aren't really people, like souls, they are just a emmission from the body, like breath. Which makes you sound even worse.
So, in my desire to write a character who has done this terrible thing, I need to allow the terrible thing to exist.
That being said: Ken's got the right of it on metaphysics. A "ghost" can be anything from a recording etched onto the surface of the sea of Vim, to a tormenting personal devfil, to a guardian angel trying to beat repentance into your withered conscience.
Sadly, the likely* perpetuator is a PC, although the victim would be an NPC. Probably.
[*Nobody's actually killed anyone yet, but the character's trajectory does look like it's heading that way, so I'm trying to come up with ideas in advance.]
I was thinking mostly of ghosts that were a direct follow-on from the original person, and particularly magic ghosts - I agree once you start getting faeries / demons all bets are off.
Is the thing you speak to when you're using Whispers Through the Black Gate actually part of a Realm (barring shenanigans)? Possibly not since I don't think it needs to penetrate?
It's got a Mentem requisite, though, and it's pretty clear you're talking to something - the spell description even says "The spirit that you speak with is not compelled to tell the truth..."