Let's assume that for plot reasons, a magus with no prior exposure to or unusual knowledge of the Infernal Realm (no Infernal Lore, etc) ends up meeting a demon in a story and killing it. Would just having the baseline expected Magic Theory score of 3 be enough to automatically assume the magus knows not to mess with the vis in the corpse, since it'll more than likely just mess up whatever they use it for? Or would you say that direct confrontations with the Infernal are rare enough among magi that they'd need to make a more difficult Magic Theory or even Infernal Lore check to know exactly how much Infernal vis messes with Hermetic magic?
Infernal vis is not common knowledge in the Order.
"Infernal vis has three types recog-
nized by students of the Infernal within
the Order; each type offers successively
greater risk in use. However, only cau-
tious magi who have a score in Infernal
Lore will be aware of these divisions, and
most magi do not realize that vis can even
be corrupted by the Infernal in this man-
ner — at least not until they suffer the
effects of its use." - p18
"Infernally tainted vis is not common-
ly known in the Order of Hermes,
for its most common source is the
corpses of demons, and those slain
with Demon’s Eternal Oblivion do not
leave behind a corpse. This gives
the storyguide plenty of oppor-
tunity to pass Infernal vis off as
regular vis." - p19
Let me put it this way. Apotropaics are professional demon hunters mastering Vim (usually) and you would think to be a pro demon hunter would require a fair level of Infernal Lore. They have the only spell to cleanse vis, which is a trade secret and they're wrong about how it works. So no, the average magi assumes vis is vis. I wouldn't even let a magi with Infernal Lore 1 roll.
Oh, somehow I stumbled right past the relevant text in RoP:I for this question. Thanks guys!
Leads me to a general concept of magi who are afraid of using divine vis taking it to a "mystic" who "purifies" it into something that spells tell them is magic vis but is actually infernal through a corrupting ceremony.
@silveroak Diabolical! I love it. I wonder if Divine vis counts as a holy thing for the purposes of profaning? In which case anyone could turn it into Infernal vis, albeit at the cost of a Confidence point.
I would expect it to use the same rules as converting a holy relic- in other words anybody can profane an item with vis at no cost so long as their confidence score is higher than the number of pawns of vis.
That would be a reasonable thing for an SG to allow, but the wording of profaning Relics is that they don't cost Confidence because they expend a Faith Point from the Relic itself, which isn't a resource shared by Divine vis.
You either have confidence creates vis (which fits with effects in RoP:M) on one side or faith points are corrupted into vis, though there are other cases (esp. faerie) where magic vis can be claimed and converted by another realm, plus infernal vis which is purified (to magic) also translates 1:1.