So in my Ravenloft game (did I mention I run a Ravenloft game?) my players hit the sewers in Port-a-Lucine searching for a hidden lair of a mad professor/wizard who worked at the local establishment of higher education. These sewers (at least in my mind) are labyrinthine and span miles, undocumented, as they predate the current civilization of Dementlieu. One of the characters is haunted by a friendly ancestor. One of the things he typically has the ghost do for him is scout dark terrible places because it's safer that way for the rest of the party. I don't see this as an abuse of the ability, indeed, it's rightly saved their asses enough times it's probably essential.
At the same time, having a 'get out of jail free' card in a horror game really isn't a horror game. In the last session, while scouting, the ghost found a Neh-thalggu. Basically one of these:
He communicated this back to the party, but being effectively someone who was just a knight, not exactly an abject monster hunter, he couldn't explain it very well beyond "the stuff nightmares are made out of", and the ghost himself got the creeps because the thing seemed to react to his presence like it noticed him. I don't expect them to go back and fight the thing. Ever. They're average character level 7, still getting shredded by
CR 3s, and it's a
CR 20-something. That's not a problem.
What I'm toying around with here though is making the ghost take (and likely fail) a Sanity check for seeing it, which will basically result in the ghost getting a fair bit demented for encountering that. There's not really any sort of precedent for non-mortal creatures actually dealing with Horror or Madness though. I'm not wanting to punish my player for having his ghost help him in an intelligent manner, but by the same token, I want to subtly reinforce the "nothing is safe" element. I wouldn't make the ghost go so crazy that he would hurt the party, and he could recover (mostly) from it given time.
From a roleplaying point of view though, this ghost is absolutely loyal to the
PC, and was the one to originally train him to fight. If I had to pick a way to handle the 'madness' right now, it would probably be through the ghost manifesting with a tentacle, or a crab arm, or maybe even the top of his head missing with a brain pod like what the creature has. The purpose of this is to try to illustrate that the ghost has become somewhat obsessive in thinking about the monster, and his constant fixation on it is actually causing him to manifest aberrantly. The really fun part about that is that it sort of implies that the ghost only appears to the player as what it's thinking about, suggesting that it might not even be his ancestor, just something that thinks it is. There would be no other ill effects I applied other than it being unsettling as feth.
So the question is: Is this too much me fething with my players, or is it an awesome way to try to get them to lose sleep?