Even though 5th Ed. made invisibility somewhat more difficult than before, I still find invisibility much too practical. With magi of equal power, it's usually very difficult to penetrate through invisibility effect because the magic resistance is usually stronger than the casting total of the detecting spell (as usual with spells targeted at magi). I'm trying to find a way to balance invisibity by allowing a more easy way to detect those under that effect.
I'm considering reinstating as a house rule the 4th Ed. clause:
"IntÃ©llego spells can be resisted but not always countered. If an IntÃ©llego spell gives the caster a vision of the target without probing the targetâ€™s person in some way, the targetâ€™s successful resistance lets him know that he is the subject of some type of detection magic. He does not know what specific spell was cast or who cast it."
(BTW, how do you see this on 5th Ed., if you cast "Summoning the distant image" and someone with magic resistance is at the room you target to, is your spell resisted by that person? Do you get to see him there, or not? 5th. Ed. seems very strict about magic resistance on magical senses, among other things. OK, back on track...)
My idea is that with the rule above in place, some generic aspect of the invisible person can be detected without magic resistance interfering. That would lead to "arms race" between detecting and masking spells, and pit spell against spell, not spell against magic resistance.
The following spell would detect the presence of human persons by the means of the existence of their bodies (Corpus):
InCo 25 "The Fellow Man Revealed"
R: Per D: Sun T: Vision
The target gains knowledge of the existence and location of human beings in his field of vision. The only practical use of this spell is to detect persons under invisibility effect. Normally visible persons are seen as usual. Invisible persons are seen as vague, transparent shapes with no details. For example, identifying them, or the actions they are currently taking, is impossible. The caster just gains the knowledge that "someone is right there".
NOTE: common variants have Terram, Herbam and/or Animal requisites to allow detecting humans behind natural obstacles and camouflages.
(base 3, Sun +2, Vision +4)
And the following would mask against the previous spell (effect base level just taken out of the blue):
PeCo 20 "The Inconscipuous Presence of the Ghost"
R: Per, D: Sun, T: Ind
This spell destroys the aspect of presence of the target's body, masking the targetâ€™s body against the InCo spell "The Fellow Man revealed". This spell is ineffective, if the sensing spell is cast with an arcane connection to the target.
(Base 10, +2 Sun)
What is your opinion, would this work, with the aforementioned house rule in place? Any way of justifying logically that this sort of detection is not resisted?
(Corpus is only one of the Forms that could be detected. Mentem (minds) Herbam, Animal, Terram (clothes and carried objects) are other alternatives.)
I'm keen to hear any insight you can give on this.