I am away from my books and have a question.
Let us say that a person is possessed by a spirit , a person with second sight would be able to see this.
Now let us assume that the possessed person is a mage and has their Parma Magica up would the second sight need to penetrate the parma magica to be able to see that the magus is possessed?
I would tend to say that you have to penetrate the magic resistance of the possessing spirit. However, the spirit could be using the magus's magic resistance if it is better than the spirit's own.
I would say that a spirit which is not trying to hide can be seen by a very low roll on second sight - eg vs an ease factor of 3-7 depending on several factors like whether the victim is a long way off, hiding their head, in full armour, etc.
On the other hand, a spirit which is hiding (does not need to be an active activity) would need a higher ease factor. Maybe the original ease factor + a division of it's might; /5? /10? /2?
(A demon/devil can 'lie' to Intellego spells. Can they 'lie' to Second Sight? Makes Sense Holy/Unholy more useful...)
I would not require a second sight roll to penetrate magic resistance (Parma or Might or other (and, as LuciusT suggests, I would allow it to use the highest resistance available)) as an actual number, since second sight is a single ability not a combination of Arts + Penetration ability.
Gilarius
I believe it was discussed before and that it doesn't need to penetrate, but I don't have my books here either.
The rules about SS are found in ArM5 p. 67 and say that "(t)he Magic Resistance, if any, of the concealed creature does not interfere with your Second Sight."
This is correct. Second sight doesn't need to penetrate to have it's effect. So, it doesn't matter; the magic resistance of the spirit and the character being possessed are both irrelevant.
In fact, Second Sight can be used as a source of insight to make Intellego detection spells that don't need to penetrate. Pretty handy to have.
Second Sight in a properly aligned Aura is very impressive, nearly impossible to use illusions or invisibility against such a person.
As for a spirit INSIDE someone...
I don't think Second Sight would apply at all. Possession doesn't really come under the heading of things Second Sight can detect.
Sure, you can see spirits, but when a spirit is hiding behind a barrier that doesn't actually mean very much.
On Demons:
I'd go so far as to say that a Demon can't 'lie' to Second Sight that isn't False, but I actually don't know for sure (I've only glimpsed at Infernal and don't much care for using Infernal in my sagas anyway). That is, its illusions and invisibility are as subject as anyone else. A strict reading of Intellego Vim suggests otherwise, but that could be a Hermetic flaw as much as anything.
Then again, for nonHermetic divination and other methods of detection, I'd say they'd be useless against demons.
Second Sight just seems like something that should work, so I suspect it's merely bias on my part.
IMS (several of them in fact) this has happened more than once. Demons can lie to second sight. They can't lie to detect holiness and unholiness. This is what makes SH&U most useful.
Cheers,
Xavi
And there you have it, demons can lie to Second Sight. Serf's Parma.
That said, I'm pretty sure possession cannot be detected with it.
More or less we use it that second sight and sense holiness and unholiness are equivalents. Only that the first works on magic/faerie and the second on infernal/divine combos.
Cheers,
Xavi
I've never seen anything suggesting that Second Sight or Intellego in general cannot be used on the Divine. It seems to be exclusively for Demons.
Sure, divine gets some fun stuff like 'NO MAGIC CAN EVER AFFECT THIS' but aside from that, no general 'made out of pure deception.'