The magi were gathering to cast the Aegis of the Hearth, when one of the grogs, having second sight, shouted out about a shadowy figure looming over one of the elderly magi. The magus himself, Oswald of Elk's Run in Hibernia, follower of Bonisagus, was too sickly to take much notice, but other magi were concerned. None of the magi were able to see this figure, not even with a serious InVi spell. A little later she saw a second figure, which also one of the magi, with second sight himself, could see. He seemed to be identical to a person who, posing as a follower of Bonisagus, had introduced two magi to a demonic cult, and was invited into the Aegis with a token two years prior by a third magus. The invitation was revoked when the three magi discussed the matter, but maybe he had stayed inside the Aegis since then. It seems that the two immaterial beings took part in the Aegis ritual so as not to be hampered by it for the next year. While there is no proof that they are demons, there are some clues pointing that direction.
So far the uninvited residents have not done much harm. One of the magi got an urge of avarice and stole two books from the private collection of a senior magus, and another was approached by one with an offer of help and support to assume leadership and «make the covenant great».
Now, the question. You know that there are two unwelcome, alien entities living inside your covenant, taking part in the Aegis ritual, but only one or two people can see them, and nobody has any spells to affect them. What do you do? What can you do?
Yes, I realise that there may be questions over the interpretation of the infernal and the aegis, and I am happy to discuss those at well.
(1) Either get a few good demon hunting magi from somewhere and trust them to save you instead of ratting you out.
(2) Or throw yourself at the mercy of the Lord, have a chapel consecrated in your covenant with a good relic, agree that the bishop will visit it up to once a year, get a good steady and reticent chaplain, and have him purge the covenant. (I assume that your covenant is in a Catholic area: if not, details will vary a lot.)
(3) Or give up the covenant and join another with a better maintained Aegis. And no, you cannot just set up a new Aegis somewhere else yourself: your new friends can follow you there before the new Aegis is up.
(4) Or just live with your new guests and hope that very few notice it.
My troupe assumes that "to take part in the Aegis ritual" means to be active participants, with the full collaboration of the magi involved in the casting. So, in general, "sneaking in" does not qualify.
I'd be inclined to say, spend a season developping Demon's eternal oblivion with an unstandard target like Room. Remind your new guests that, even if they somehow can slip through your Aegis, they still suffer the negative effect of the aura to their Magic Resistance while you gain the bonus to spellcasting. If the covenant aura is already dominated by an infernal aura... screw it and move on, or fortify a small part of the covenant under magic aura with a new aegis cast on a non-standard date, and use that location as the base from which to fight from.
Demons are a very YSMV subject, since some players enjoy it and some hate it. The way chosen, injecting them directly into the covenant and inside their defenses, is one of the harshest methods possible.
Sneaking demons in when the players were not expecting them and have zero ways to counter them will have several knock-on effects. At the very least some of the Magi will drastically change their long term development plans. At the other end of the scale, the saga can come to a rapid end. The most likely thing will be a significant disruption of the saga as the players try to figure out how to deal with it and possibly move the covenant.
Unless the game is slow moving, you are going to end up with at least one Magi who can burn demons to the ground. DEO variants with non-standard targets will be acquired/researched. The wildest I have personally seen is a DEO Ritual with T: Boundary. Wards are going to start being researched and installed all over. The players/Magi will get paranoid.
My current game ran into a moderately powerful demon (Might 45) and I had the misfortune of being the best ReVi and PeVi. So a non-combat Boni (combat?! Ummm, I have one spell) went from nothing to being able to erase that Might 45 demon form existence in a single round.
Since you describe this as harsh, I should mention that this started with one magus with Plagued by Demon. When the demon tried to trick him into worshipping a false god, another maga immediately subscribed to the idea. (The prize was Mercurian Magic with a much easier initiation than that of Primatius, and better affiliated with their non-Roman pagan beliefs.) When they discovered, the magus went on a kamikaze mission on the Cult, and the maga already at that point turned towards the demon hunting focus that you describe. From that point I guess you can see the snowball effect.
IOS, the bulk of the officers participate in a bounding walk, tracing the terminus line of the Aegis. Demons may be mingling in such a group, or possessing one of them - in a previous saga we had a maga who had her faerie pals join in, which we found pestiferous but barely tolerable.
IIRC, the Aegis defines a line. Supernatural beings inside the Aegis boundary are not expelled, but if they leave, they can't re-enter. Perhaps that is what is going on. They're stuck inside, but willing to be.
If we discovered there were probably or certainly demons inside the Aegis lines, we'd probably fumigate heavily with salt, see if we can get a friendly priest to bless or even exorcise, and, once expelled, install an infernal-repelling device of some kind, probably a bell.
If they can actually partake in the Aegis ritual as it is cast, they would no longer be stuck, and their powers would not be penalised, but yes, this is the reasoning I depend on.
Yes, I agree that partaking in the ritual is not well-defined. The magus who sneaked away to rob a private library missed the middle part, but I am going to assume that the beginning and the end suffice to count as partaking, so that he does not have to ask for a token and an invitation ...
Re-reading the Aegis of the Hearth, it occured to me that, while it is customary for everyone in the covenant to walk arround during the ceremony of the Aegis of the Hearth, doing so has actually no mechanical effect, except for participating magi. Ergo, casting the spell may not expel them. But walking arround invisibly along with the magi doesn't make the demons immune to the negative effects of the Aegis itself, which would require an invitation that can be rescinded at any time by any local magi. Unless there's a covenant member re-inviting them on a regular basis despite the lack of consent from the rest of the covenant, their powers would be doubly suppressed by the local aura + the aegis, which may mean that they are harmless except in regards to whatever natural weaponry they may have unless their Might is very high.
I agree that this is a valid interpretation, where one assumes that taking part is an active act in the ritual. You seem to imply that it is the only valid interpretation though, and then I wonder why? To me, taking part, could mean any number of things, including just being part of the token procession. What is it that makes you confident that this is the interpretation of Aegis?
All sections that confer immunity to the Aegis powers based on participation in the ritual are confered only upon magi and non-Hermetic wizards (3rd paragraph, penultimate paragraph)
The effect on creatures with Might is described is defined in the fourth paragraph only. All references to removing the negative effects of the Aegis upon creatures of Might depend on an invitation that may be rescinded at any time. Those invitation can only be handed out by someone who participated in the casting of the Aegis. In other words, it requires a magi's consent here also. The only part that doesn't require their consent is staying within the Aegis if you were there when it was cast.
The references to the whole covenant participating in the Aegis, in the penultimate paragraph, is purely descriptive and marked with the word "usually". In other words, it may or may not happen, and having the whole covenant walk arround is a tradition, not a requirement of the ritual. If it's not a requirement of the ritual, and there is no descriptive effect that separates covenant members that walk from covenant members that don't, then there is no impact of walking the ritual or not walking the ritual - unless you have the gift. The benefits are confered on participating magi.
Basically, demons don't participate in the casting of the ritual, and so have no control over the wards. The wards are fully in the control of the casting magi, that is, unless you decide to grant your demons some Muto Vim ward-warping powers of some kind. Of course, the demons, not being schooled in magic theory, might very well think participating in the ritual helps them, but by RAW, there is nothing in the spell that says so.
That is pretty close to my group views it. We do specify that the AotH negatively effects the Casting Totals of Supernatural Virtues (with the exception of purely sensory ones like Second Sight and Sense Holiness/Unholiness).
There are three effective tiers that people and beings can fall into when dealing with an AotH. Participated in Casting (can Invite & Uninvite), Present During (not effected unless later Uninvited, can Invite in special circumstances), and Others (effected by, can be invited by Participant or special circumstances).
The special circumstances are generally a guard Grog who was present during the casting presenting a token to visiting Magi. While not expressly defined in the spell description, it is strongly suggested multiple times across the varies AM5 books. They can of course be Uninvited at any time by someone who participated in the casting. In our saga, the Grogs with this duty must be given the tokens by someone who participated in the AotH. In effect, the Magus are delegating a limited number of Invitations by the passing of the tokens.
It is noted that a Magus who participated can Uninvite someone at anytime, even if the being being Uninvited has a token.
The AotH is very complex and hashing out how your group will handle it for a saga is generally a very good idea. It takes up the better part of a page in my groups "House Rules & Clarifications" document, including things like it specifically not knocking down a Magi's Parma Magica and how it interacts with Regio (an important consideration for us, since our Covenant is on a massive multi tiered Regio).
Actually, no. The power to invite is granted to «one who participated». No restriction to magi or wizards there. If we really go by the letter of the law, anyone can participate the casting and then invite themselves in. More importantly, I think, is that this would mean that a familiar cannot be part of the casting, and must be invited in later. I am quite confident that that was not the intention.
2-3. This assumes that participating in the casting is something different from taking part in the ritual, i.e. there is a ritual that is separate from the casting. While it is irrelevant whether non-magical covenfolk take part or not, does not mean that the ritual they take part in when they do is different from the casting. RAW does not say that the two are different; a possible but not necessary interpretation.
Your argument hings entirely on defining participation in the ritual as different from participation in the casting, which is possible, but not dictated by RAW.