If there are 12 House Mercere Magi, how many members of the bloodline must there be? Since the Gift is not genetic, you are looking at 60,000 over the lifetime of a Magus (roughly 150 years). Without longevity rituals you would be looking at about 20,000 alive at any one time. While originally the House had those with none of his blood, in 1220 there is more than enough that the majority should have at least a fraction of his blood.
This is one of those issues that comes up with how rare the Gift is. It is common throughout the line to have some number of individuals which seems totally fine at first glance but makes no sense when you look at it through the lens of how rare the Gift is.
EDIT: If every Redcap had his blood, you are looking at only 0.75% of the known and tracked people with his blood alive in 1220. I grant that all 150 currently active Redcaps are not of his blood, but those that are not were admitted because they were exceptional rather than needing bodies to fill the role.
Just because the gift does not reliably transmit parent to child does not mean that it doesnât seem that certain lineages produce gifted children with much more frequency. Mercere himself seems to be one such person considering he trained at least two of his own children who were gifted. Also, not everyone in those families is going to be a redcap. This is more about choice of a non-gifted apprentice than about how widespread the family needs to be to produce x gifted children by 1220.
Even if every person with a speck of Mercere's blood is ten times as likely to produce a child with the Gift, you are still looking at 2,000 people with his blood alive in 1220.
In HoH:TL it says that Redcaps with his blood are given preferential treatment. For such a family focused group who gives preferential treatment to members of the bloodline, there would need to be something special about a potential apprentice who is not of the bloodline to take them on.
Additionally when talking about House Mercere you are talking about much more than just the Magi and Redcaps. In their "Mercere Houses" a large proportion of the population of normal "coven folk" will have his blood. Even at 10x the standard rate you are still looking at 2,000 tracked individuals who are "family" and they are very family focused.
Any given Saga can use whatever rate of blood to not blood they desire. I personally find having anything but the majority have some degree of his blood makes little sense. But then I also disagree with the default 1 per 5,000 rate for the Gift since it would make it virtually impossible for the Order to be the size they are. Never mind all the other groups seeking out Gifted children.
The fact is that where magi come from is intentionally left both vague and unknown- lineage may play a part or things which coincide with lineage (for example, if diet during pregnancy is a factor and your family has tradition of a particular food to ease morning sickness) Astrological sign could also be a factor, and for a given couple there is a tendency for children to be born in a given season, but only a tendency, which may relate to anything from lifestyle to the natural rhythms of the woman's body. Also note that genetics in Mythic Europe do not work like the real world, being more of a weighted Lamarckian system with unknown variables that allow for generation skipping traits.
My suspicion is that a lot of redcaps may be the non-Gifted children of Magi, which hypothetically reinforces the chance of Mercere having Gifted offspring and gives a way for Magi to pass on their social status to their children.
A magus is given a voting sigil once they gauntlet (Tremere sigils are held by their masters, but they exist). If you expect to attend Tribunal and vote, you need one. You might need one to simply attend. You do not need one under most other circumstances, but if you don't have one at Tribunal, you can't establish yourself.
A mundane mortal fake, claiming to be a magus, shows up at a covenant. They are unannounced, probably, and not known to the magi. That's not so odd. However, their Latin is mediocre, they have limited if any knowledge of the traditions and ways of Hermetic society, and they do not make any of the mortals uneasy. None of these things is necessarily a giveaway, but together it is odd. The fake is in trouble.
A fake might be able to plant themselves as a Ex Miscellanea hermit, who hems and haws around questions of lineage (it's normal to assert your parens or sponsor), or a wandering mage, but why go to the trouble, considering the penalties?
We cannot really answer this before answering why this being wants to pass as a member. To the why are are about 1001 answers, one for each of the 1001 stories we would want to tell about such a masquerade.
Let me add a few examples.
Deluder demon
A deluder demon actually made its appearance in our saga, responding to a PC's story flaw (plagued by). This deluder wanted to recruit magi into a false cult to promote sin (etc). Knowing that the magi were keen a on Mercurian magic, the demon took on the identity of some fictitious magus, and put a book on cult lore written by himself into circulation. The cult was designed to fit the PCs ethos better than canon Mercurian cults, of which there are so many, that one more does not disrupt the balance of things.
Now, a deluder's masquerade is not supposed to be perfect. There were give-aways, and the players and the characters did discover it, but only after their first warping points. When you get a book on an Hermetic topic via a sodalis (in this case an unsuspecting NPC), you do not immediately quesiton the identity of the author. When you meet a presumably senior magus, you do not immediately test his powers. Only over time do the minor give-aways pile up to suspicion, and the sodales start to devise tests. @dc444 could say more about how and how soon the players realised the infernal plot.
In this case the demon had no interest in fooling the Order as a whole, or pass as a magus at tribunal. He only needed to pass as a magus to a limited group of magi for long enough to reel them in. He failed, but that was mainly because I made the infernal plot too naive.
The hedge wizard
This only came up as an idea in the saga. The antagonist (Herrick from the 2ed The Tempest) had other lines of attack than actually joining. He did, however, enquire about the possibility of joining the order. This is, honestly, quite straight forward. If he can demonstrate sufficient magical ability, the Order is supposed to admit him. You just need to find a sponsor in a recruiting house, i.e. a suitably aligned societate, which usually means Ex Misc. There would have been nothing to stop him, and he would have been a legitimate member bound by the Oath.
(This story had the side effect that the players never again would try to broker membership for any pleading NPC, no matter the circumstances.)
The Covenant Intruder
This last example is one which worries me. Hospitality is expected in medieval Europe, and at least in most tribunals of the Order. Magi are supposed to be able to show up the covenant gate expecting lodging for the night. An impostor, with no intention to infiltrate the Order, could pose as a sodalis to this covenant, who would have absolutely no way to check their claim.
OK. Aegis tokens would not usually be expected or offered (with a few exceptions like Qui Sonant in Hibernia), so mighted beings would struggle. Anybody else could manage with some acting skill.
I am not sure what this tells us. Possibly that any prudent covenant should have guest quarters which are securely separate from any rooms containing valuables of any sort. It seems so clear that such an impostor cannot be kept out, that the question becomes how to accept them without risk.
Concluding remarks
The success of masquerading depends very much on the contexts where you need to masquerade and how much you need to push the limits. An impostor with modest goals and who avoids risks and imposes only where they have something to gain, can go undetected for a very long time.
We, as players, began suspecting after we met him but before we actually took part in the ritual. It was confirmed to us as players after the ritual because we now had the False Power flaw. As characters I think my character was not sure until the other character was and left us a note before foolishly attacking the cultists and the demonâs other minions on his own. I do not remember how that character came to that conclusion.
Re: Your hedge wizard thing - that one only worked well because we were in Hibernia and hedge wizards have a modicum of protection in that tribunal.
An interesting possibility would be some random escaped peasant who has discovered that he can travel from covenant to covenant, pretend to be a magus and get excellent room and board for the night, probably pocketing enough food to last him for a couple of days beyond his stay. Could go unsuspected for years (possibly even develop a reputation as a wandering magus) until he triggers some plot point.
A random peasant is unlikely to pull it off, for lack of knowledge both of the Order, its customs, and its Latin. A random member of the impoverished clergy could do it though. It only takes a little experiences from the right circles to know enough to bluff the rest, and I think it works no worse for the story.
Not right away, but if the peasant is a decently accomplished con who manages to pick up rumors of the order and establish enough lore knowledge to pass himself off while keeping his head down and ears open...
I agree that the right kind of peasant could pull it off, but to me, that would be a most non-random peasant.
Picking up enough Latin would take an exceptional talent, or some sort of unpeasantly experience. A maid from any learned household with regular dealings with magi could probably play the role well in her own language, but she would depend on some special circumstances to hear enough Latin to actually speak it.
Latin would be the easy part- if they can get a season or two of practice with people who speak latin they will be fairly passable. That gives them clergy, academics, magi... Latin is the most widely spoken "dead" language in mythic europe and it would probably be easier to learn than a truly foreign language in most areas.
order of Hermes lore would be the harder part, and again that can be "practiced" with the head down ears open approach.
actually picking up artes liberales may be outright impossible.
Order of Hermes lore is easy, because so many magi focus so much on their arts that they to suck on their own lore. You can play a rank-and-file ignorant magus passably with little trouble.
Latin is hardly spoken on a daily basis, is it? The parish priest may know Latin, but whom would he speak to? Academic discussions at monasteries, universities, and possibly at bishop's sees, yes, but would they use Latin in everyday conversation like we tend to assume the magi do? OK, maybe that assumption is just legacy from 3ed when magi started with a better score in Latin than their mother tongue. Anyway, it is hard to pick up Latin from an academic conversation when both language and contents is strange. Possible, but exceptional talent and exceptional opportunity.
In many universities - yes, they certainly would use latin for everyday conversations, because with people from many different place they would not have any other common language.
biggest opportunity would be at a university- try to listen in on lectures or study groups while you get the hang of things, pretend to be a poor student instead of a poor escaped peasant. You learn language and hear rumors of this group that recruits the academically accomplished and actually provides a decent standard of living...
I think people underestimate how one's social upbringing colors the way one thinks and behaves in general, as well as affecting how we relate to others of a different social status. Nowadays we take social mobility as something positive and possible. That was not so at the time.
A peasant would act in innumerable small ways that would scream "peasant" to someone from a different social class (nobility, academics and magi). He would need to be coached for quite some time (seasons, perhaps years) by someone who is very familiar with the social status to be impersonated. Achieving such a result unassisted would take many years of exposure, driven by a keen mind and sense of observation (high-Int, high-Per) to notice and remember all of the details of how magi are expected to act and speak to each other.
We have a saying around here: "You can take someone out of the countryside, but not the countryside out of someone."
on the other hand anyone even considering attempting this has, by definition, already overcome some of those conditionings.
I agree that the hypothetical peasant will not be the norm by any stretch of the imagination, but I do believe they do not have to be extraordinary from a game perspective- a high guile score takes care of most of the "tells" and then it is a matter of figuring out where to pick up the related more exotic abilities. Obviously actually learning magic is right out.
That is very true, but there are a couple of exceptional circumstances which can make things work. Some servant children happen to grow up with the noble children when the parents are looking. There are the jesters and entertainers who move more between social classes than most others, and most importantly learn to act a role. And then you may have the nobles who fall on hard times descending into the peasant class.
A dedicated group of powerful Infernalists could collectively imitate a Hermetic Magus using Ceremonial Diablerie to take turns granting themselves the False Gift. Effusion can change their appearances to make them look, essentially, like the same person. If one of them can have their arts opened as a hermetic wizard by some means, then they would all be able to simply take turns opening the arts of the other. They would just appear, claim to be a hermetic wizard from a distant tribunal, display their powers (and thus proof) and show a random symbol as their "sigil". Once they do this, they can just quietly steal whatever knowledge a covenant has available to traveling magi.
The reason, of course, they take turns it to avoid the problems offered by the Gift- each of them takes the burden for a year, incurring heavy warping from the dark enchantments they must lace through themselves.
Naturally, this is a level of coordination (and knowledge of the order's inner workings) that would be very unusual for a group of Infernalists- they would likely have some kind of patron who is providing them with both advice and preventing the group from fragmenting. Perhaps a exiled Diedne wizard who uses this to keep up with the current hermetic literature by having her coven of infernalists learn and then write about the arts. Or, perhaps, a hermetic sorcerer who plans on killing them all at a later date, then summoning and ablating their ghosts in order to pour all of their knowledge regarding the hermetic arts into herself.
Having a hermetic patron who is guiding you would, of course, make everything a lot easier!