One of my players recently asked some questions that made me question some long-held assumptions about vis, particularly regarding InVi detection spells and learning from vis.
The last part of the InVi sidebar in the ArM5 core book says raw vis will show as 'magical' under magical investigation. There are no spell benchmarks provided for determining the Realm of vis. Despite this, there are instances of vis of different Realms being treated differently from a rules perspective, like Faerie Magic in HoH:MC. I've always assumed InVi would show you the Realm of vis, but that doesn't seem to be the case. How does a magus know what type of vis he's working with?
In a similar vein, if all vis is just 'magical', does that mean a magus can learn from any type of vis? I assumed it had to be Magical vis, but now I'm not sure.
I would personally use a level 4 guideline as with other vis-clarification spells, along the lines of Sense the Nature of Vis, called Sense the Realm of Vis, with the obvious reminder that such a spell would still be subject to the limit of the Infernal.
I'm not sure off the top of my head about learning from vis, but I would guess that any time of vis would do. Monster-hunter types often hunt hostile fae and I think their vis would still be eligible to learn from, etc.
Rules for Vis use are all over the place. Generally we have assumed that detecting Vis is easy enough, but the realm may not be apparent with out a Lore roll or more spells. Generally we have also said that most Vis can be used by Magic characters, but that either botch dice are added (which is the standard for using exotic realm vis) and/or other issues with the magic may occur when using exotic vis.
As a clarification: I was under the impression that the Limit of the Infernal specifically applied to demons, and not to their servants or tainted things. Was I mis-understanding, or am I just remembering and mixing up different rules? Sadly I only have access to the core book right now and can't look up anything in the ROP:I.
It's one of those things that's never been comprehensively or consistently explained, to my knowledge at least.
The following spell from RoP:I further muddies the waters:
Apparently Hermetics CAN detect Infernal vis in the wild, or they wouldn't cleanse it via this spell, but they can't detect the Infernal taint after casting the spell. Alternately, Hermetics can never detect the taint and just go around casting the spell on all vis, in munchkin gamer fashion, despite the chance of eventually botching and damaging themselves.
Hermetics can be quite logical, and demons can be quite tricky, too. For example, if you slay a demon-tainted size +2 giant frog, and you know its infernal, you should be smart enough to know its vis is tainted, and cast to purify it. Demons deliberately creating infernal vis themselves I would argue can't be detected by hermetic magic. An infernalist sacrificing black goats over a stone to make the stone into vis probably would be detectable, if my metric is correct.
All that said, I may be misinterpreting things; That's how it always worked in my saga, however.
How do you know you killed it? It could be faking. Then make some normal Vis look like whatever. It is annoyed you tried to hurt it. You can't detect it following you and place Infernal Vis in an acorn and make it look like like an Acorn of Virtue.
If you can't detect them because there is nothing to detect. The human mind does not have the ability to see the thruth of things like angels/demons without Divine aid.
I would venture to guess all the spells to damage demons and contain them don't work at all and instead just communicate that one has no Divine power.
You want to bind a demon, sure it pretends you bound it.
You want to purify some Vis, sure, you purify it. The only reason it isn't pretending the Vis is Faerie is because you would get suspicious.
If I were The Morning Star I would disappear and not exist, mandate all lessers take the guise of Faeries. With nothing to scare mankind into god's loving arms, man will turn away himself.
Demons do not have perfect information. If the demon doesn't have a high score in NeoMercurian Cult lore, someone who does have such a score might certainly notce that the alter was irregularly or incompetently done. Demons have supernatural lying powers, not supernatureal knowing powers.
ROP:I specifically states that Hermetic abilities can detect infernal influence- for example auras, unless a demon is present and actively working to hide said influence. A diabolist would need a full time demonic assistant to avoid magical detection, as would a hypothetical demonic acorn.
As with the case silveroak pointed out, it is stated many times that faerie/magical (and sometimes explicitly Hermetic) magic can detect the infernal if it's strong enough. However, it is also repeatedly stated that being Tainted doesn't show up, while Divine and Infernal methods detect Tainted. This doesn't work with demons themselves though. So, is the vis strongly infernal or not? As there are three different levels, I would base it on the different levels myself. I would say Vis Infesta is just tainted and thus below this threshold, while the other two are detectable based on all their descriptions.
They have the natural knowledge attributed to all Angels present in creation. It is diminished as not all is was shared before the fall, their speculative knowledge from revelations is intact. The knowledge of charity etc. they are devoid.
I.e. They know a lot.
Thier ability to deceive, if one grants them said ultimate deception, then extends into corruption of speculative reason. As we all know Reason's doctrine which includes the law of causality and ex nihilo nihil fit, collapses under its own contradictions already. Manipulation of memory to further corrupt conclusions derived from speculative reason are child's play.
Anything short of Revelation is corruptable.
Typically the "inability to detect" demons and indecernable ultimate deception I think really should be ignored, because otherwise the game goes off the rails and becomes all about Catholic theology.
This seems reasonable to me. Hermetic Magic should be able to detect the Infernal, other than that specifically hidden by "demons", whatever those are defined to be. I would not call everything with Infernal Might a demon but others may feel differently. Taint, including powers influenced by the Infernal but actually drawing on other reams, such as - I believe - Goetic Summoning, is not detectable by Hermetic Magic. This may be a minor flaw in Hermetic Theory, although other magics (but not Divine powers) seem equally unable to detect Taint.
I would still differ from the printed spell. If Taint (such as Vis Infesta) is not visible to Hermetic Magic, it should also be uncleansable. I absolutely hate the ways in which Hermetics are described as getting around Infernal and Demonic undetectability by using Techniques other than Intellego. Demons should either be visible or invisible to Hermetic Magic as a whole, not simply to the most logical Technique for detecting them.
I get where you're coming from with the rest of your statement, but this seems to jive with other canon stuff. For instance, you can't detect a demon, but you can cast Demon's Eternal Oblivion on one. I'm guessing from the rest of your statement that you don't like that, either. However, we know the pairing of demons being undetectable but destroyable via Hermetic magic is definitely canon.
Demon's Eternal Oblivion's realmeffect : notifies a demon the Magus thinks he can hurt it, time to play pretend.
Hermetic magic has no verification the spell worked.
From my perspective take demons out of the game or make them detectable. Demons can be anywhere and everywhere. They don't have to babysit an aura. They just need to know when to be there. Darn they were late and you figured out something. They change your perception of events.
True enough in canon. I do see a distinction between understanding the Infernal enough to do crude damage (DEO) and being able to actually change the nature of Infernal Vis but that's certainly debatable.
Outside of canon, I would suggest that Infernal things that can't be sensed also cannot be targeted, even by area effects. In effect, the Demon's nature would allow it to hide from Hermetic Magic until it's otherwise revealed.
This has rapidly turned into a 'What Can Demons Do' thread... Which I'm okay with. Still, I feel we can codify this better. The RoP:I book goes pretty in depth into what demons are capable of. There are a few points I'd like to check on.
RoP:I specifically says that "demons have lost the state of pure intelligence possessed by the angels...", so they definitely are now bound to making mistakes of logic and reason.
Is this something you feel SHOULD be true, or do you actually have that stated? RoP:I does explicitly state that you can attack a demon's might with PeVi, but the hard part is sensing it if it's non physical. You can trick them into doing an action that reveals themselves, since they are Essential liars, not Essential lie detectors. Their mental stats are bound by surprisingly mortal means, though they do tend to have higher numbers than average mortals - Magi are notoriously better.
This part is true. I certainly imagine demons pretending to be destroyed when it fails to destroy them, or pretending to be immune when it succeeds in reducing their might.