Figured I'd start a thread about the stories that will be told, as a sounding board regarding their nature before they are implemented. So feel free to chime in on the stories you want to tell regarding your characters, and comment on other players' stories.
Story Name: The Lost Summa
Character Cast: Petronius, Rufus, Katherine, a redcap, possibly another grog or companion
Synopsis: A summa that was promised to Laurus Argenti goes undelivered, yet the covenant who pledged it at Tribunal says it has been sent. What happened to it? Petronius, as the magus who arranged for a copy of the summa in question (The Manipulation of Mystical Forces), will investigate the situation.
First will be an exchange of letters with the covenant who promised the book (perhaps Fengheld). From those letters, he will learn that the book was sent by redcap. Except that the redcap in question never arrived. More letters to friendly redcap contacts, which will raise the fact that the redcap is missing.
So, along with the redcap who delivered that latest information, and a few grogs, Petronius will travel to Fengheld and together they will try to retrace the steps of the missing redcap. Unfortunately the man is dead (reason of his death to be determined), and his belongings where remanded to the local church. Is the book amongst them, or was it stolen? If the book is there, has the priest begun reading it?
And if the priest is reading it...is he making any sense of it? And if so...how?!
The priest having the book is just one possibility. It can as easily have been taken by those who killed him (if applicable), those who found his body, or someone else. I'd rather leave it open at this point.
As this is something of a treasure hunt/recovery, it may be more interesting to build the story if I (as Petronius' player) don't know everything about it in advance.
So, would someone be interested in providing information at various points in the story? I can describe most of the details as I write the story and interactions, but having someone else inject previously unknown information into the story would certainly make it interesting and unpredictable.
Other players are also welcome to play some of the secondary characters, like the redcap or Katherine, or insert one of their own. So long as it is understood that the main character remains Petronius, this might enhance the story by adding different voices. I'm simply not sure how this will play out in practice, as this is an experiment. 
Are you looking for someone to fill in the cause of the redcap's death, the location of the book, or both? Would you be looking for a mundane cause, or a more magical one?
I was thinking along the lines of a mundane reason for the redcap's disappearance -- bandits, sickness or simply an accident. The story is a cautionary tale that even an experienced traveler can meet an unfortunate end, no matter how well prepared.
The cause of his death would simply provide a false lead into the location of the book.
For example, one scenario would be that he was killed by brigands, with his possessions ransacked. The body was later found by a peasant from a nearby village. His body was brought back to the village for burial, and what was left of his possessions remanded to the village priest. The priest claims there were no books in what he was given. All points to the brigands being the ones who took the book, but if they are chased down they don't have it. Whether the priest lied, or the brigands sold the book off to someone else, or the peasant who found the body kept the book, are all possibilities in this scenario.
Another scenario would be that the redcap became ill while staying at an inn. This may be a natural illness, bad food, or murder by poison. The innkeeper tried to help by calling upon the local herb-woman, but they could not save him. So he was buried in the local graveyard, with most of his belongings given to the local priest... The book may have been kept by the innkeeper, the herb-woman, the priest, or someone else totally unrelated.
Overall, I was thinking that tracking down the redcap's body would be easy -- a spell cast at Fengheld, or an item, or simply following his usual route. But he has been buried in consacreted ground, so his ghost cannot be called. Locating the book will be more troublesome.
A few things to keep in mind regarding Petronius' capabilities:
- His Gift is not gentle.
- He has very power in investigation, and has difficulty doing spontaneous magic (as a Mercurian it takes 15 minutes per magnitude).
- The best he call pull off is a 2nd-magnitude InCo or InTe spontaneous spell. So most of the things being investigated here would need to be done mundanely.
- He may also be able to pull off 2nd magnitude spontaneous spells in Rego, regardless of Form.
- He also has few formulaic spells that can help him here -- probably only Doorway to Doorway (short-distance teleport spell), Lamp Without Flame and The Crystal Dart may be useful at some point during the story.
- This may be compensated a little by enchanted items owned by Horst, or recovered from the dead redcap's belongings.
- Otherwise he will have to rely on his mundanes (grogs, Horst). Rufus is more of a wild card, with whom he cannot talk yet.
In short, the solution to the story should be relatively simple, perhaps only requiring the will to investigate all leads until one pays off.
A general question: How do we want to name/number the stories threads?
For now, we seem to be using the format "Chapter [999]-[Name of the story]". Does that suit everyone? Do we want something to identify which of the character is the "main cast" of the story?
Just wondering what people prefer/feel more comfortable with...
works for me
Did Sigmund ex Mercere have a horse or any other special items?
I have some ideas about what might have happened, and will be happy to throw in a curve ball, if you wish. It won't be anything fancy. Chances are, Kat will have to do most of the talking, given Ortolf's appearance and your gift.
Would you mind if I played Ortolf for a bit?
I have nothing specific in mind for Sigmund, so if you want him to have or not have anything, he's wide open. Petronius did not know him personally. He may have been a less experienced redcap, or was simply unlucky.
JL mentioned that he'd like Alips to come along, so she can do part of the talking. I was also thinking that Horst of Mercere (from GotF, but we can flesh out a younger version) would probably join the search, so he might also do the rest of the talking.
And you can certainly take control of Ortolf for a while. He's there to be played, and I don't expect to handle all of the grogs I detailed. 
Next steps for The Lost Summa ...
Petronius can pick up the trail at two possible places:
- The church of Saint Stephan, where Sigmund is buried, in a small hamlet west of Limburgh. Father Engelbert saw to the burial after Sigmund's body was brought there, along with a pack pony and message bag. Father Engelbert is middle aged, and worried about a statue of Saint Michael recently arrived with a broken wing from Saint Stephan's church in Mainz. He saw to Sigmund's burial, but was not sure whom to notify as the letters in the message bag were not addressed to people or places he understands. He knows that Sigmund died at a local inn, and can direct Petronius there. (The book is not in the message bag.)
- An inn known to the locals as "The Empty Tankard" as the father of its current proprietor was not the best at making sure he had sufficient stock. Heinrich the innkeeper is much more business minded than his father, but the name has stuck. Sigmund was brought here, with a grievous head wound, by a stone cutter and his son. The dog, Max, which appears to be an Irish Wolfhound, can be found in happy residence at the inn. A healer, Dietlinde, attended Sigmund for three days, but despite her efforts, he died. Heinrich took the body and his belongings, including the pack pony and some silver to Saint Stephan's for burial.
Is the intent to have Sigmund been buried in a small church?
Otherwise there is the impressive Saint Lubentius Basilica close to Limburg, about 2 miles east, in the village of Dietkirchen. (I have added a link to it on the wiki page for Limburg.)
I have the germ of an idea for a story for Aedituus.
The story starts with some correspondence between Brother Clement (the herbalist at Laach Abbey when Aedituus visited there four years ago) and Aedituus, whom Clement knows as Brother Abelard. The two have been exchanging letters since they met. Brother Clement has become Abbot Clement, and is faced with a difficulty at the Abbey with the death of the Infirmarer, and wonders if Brother Abelard might come and help during the busy winter months to care for the sick and aged. Somehow, Abelard's new profession should be revealed. Clement knows that Abelard has joined a community of scholars, but is not really aware of the magical side of things. The idea here is to explore Aedituus' relationships with his faith and with Clement. I ultimately want the two to be on friendly terms; this might also be a chance for Clement to rid the Abbot's library of that book about ghosts collected by one of his predecessors, Abbot Fulbert, who according to this source http://www.newadvent.org/cathen/09658a.htm did good work for the library and promoted scientific inquiry. I have it in my mind that the herb garden and cottage in the abbey are part of a lacuna that avoids the Dominion aura, but I am not entirely sure what to do with this.
Thoughts and ideas?
I would probably need someone to play Clement.
Aedituus would probably live at the Abbey for a season, without any grogs.
My first intent was that the church be small, but Saint Lubentius Basilica has some nice history, and could be worth some exploration all by itself... I don't think it matters much, other than I would prefer there be no major construction projects at the Basilica at this time. The only other difficulty is that the church has custody of some of the letters Sigmund was carrying; Petronius and Horst may have a more difficult time regaining these from the larger staff.
The Clement-Abelard idea sounds nice. You can make a demon of disease responsible for the death of the infirmarer: he was good, and the demon wanted to be rid of him. Now that there is no infirmarer he is having a field day and quite a fe people are getting sick due to the work of his minions.
If Clement is a new abbot, there might be a deal of resentment against him by other monks that were trying to get the position as well. One of them might be the ally of the demon and the one that killed the infirmarer to please his patron, that now is trying to get rid of Clement. However the relic that Clement has is proving a tad powerful for the demon, so he cannot make the new abbot fall sick. Yet. Until the relic is stolen...
The lacuna sounds good, but if you really want to up the stakes you can make the herb garden either a weak magic aura (so the plants there are useful for Mythic Herbalism) or even a vis source. Maybe a divine-inspired vis source aligned to healing so that healing magics are not affected by the divine aura.
The story with Clement at Laach Abbey does indeed sound good, as does the idea of using a demon of disease responsible for the death of the infirmarer.
Have you thought, however, about making Clement a subordinate instead of the abbot? First, he may be too young, and without the political connections, to occupy such an important role. Second, having Clement learn that Abelard is actually a magus while the abbot himself doesn't know makes for interesting future stories. It also means that Aedituus remains constrained by a degree of secret.
Clement could instead have a reasonably important role at the abbey, such as the librarian or the head of the choir. Or perhaps even the new infirmarer, newly assigned to this role and faced with such frequent sickness that he asks for help from Abelard. (BTW, switching out The Chirurgeon's Healing Touch and replacing it with Purification of the Festering Wounds might be more useful for such a story. Since the spell has never been used, and we are just starting play, I don't think this would be a problem. It would also explain why, with a Chirurgy and Medicine both at 1, Aedituus feels that he can still help with the sick.)
The demon could have a manifestation similar to the carbon dioxyde bubbles from the eastern end of the lake, and be a Medium source of disease (as per ArM5 p.180, causes a Medium wound if a Sta roll of 6 or 9).
As for a lacuna... I'm not sure. Perhaps there is a cave entrance beneath the garden? An old volcanic vent, or a water-formed entrance that leads to the volcanic tubes (at least some of them) inside of the mountain?
I'd be willing to play a role in the story. 
Arthur: If such things matter, congrats on the 1000th post!
Thanks for the response to the idea; this gives me quite a few ideas to flesh out the story. I am not used to "going infernal" and I will need to think about that, especially given Aedituus' difficulties with Perdo.
As I think about the mechanics behind a wizard and a demon in a monastery, I find I have several questions ...
- Aedituus has the Sense Holiness/Unholiness and Second Sight supernatural abilities. Given the background stories, might these be divine in origin, and thus not susceptible to aura interactions?
- In reading the descriptions of demons in ArM, the descriptions seem to imply that demons cannot enter consecrated ground... Then how would the disease demon enter the monastery? One thought I have is that there is a grotto in the herb garden with a crack in the rock that ultimately leads into the Laacher See caves. The effluvium from the magic/infernal auras in the caves interferes with the divine aura at night, creating a lacuna in the area from sunset to sunrise. The demon only comes out at night.
- What would be reasonable aura ratings within the monastery? I'm thinking the basilica itself would have an aura of 5, with an aura of 3 in most of the surrounding buildings, and maybe a 2 in the herb garden, cottage, infirmary, and orchards. This seems in line with the guidelines on pg 188.
- Aedituus is going to have considerable trouble casting helpful spells in the infirmary, given the aura. To cast a level 20 CrCo (CHT or PotFW) his casting total of 19 would be reduced by 6; not easy to cast. The level 10 Circular Ward against Demons would likewise have the casting total reduced to 13, making it difficult to cast the spell with enough left over for penetration. Attempting to destroy the demon would have to be a sponted PeVi. Aedituus unmodified casting total would be 12 plus a die roll. Divide by 2 for the deficient perdo, then by 2 again for a fatiguing spont and there's very few demons he will be sending to oblivion. And that's not including the aura modifier for being in the monastery.
I may simply go with the bad air coming from the back of the grotto, or some other such problem to be solved. Still plenty of role-playing opportunities as Clement discover who Abelard really is.
They can be divine in origin. However, since the divine is the "trumps all, wins all" realm of Mythic Europe, I prefer to keep it limited. Maybe have only SH&U as divine?
Demons can enter consecrated ground. There are dozens of stories about demons talking to priests IN A CHURCH. What happens is that they do not LIKE it because it impairs them heavily (3*aura) and are likely to feel bad there.
In any case you do not need to have them enter the ground. As long as the monks are LEAVING the abbey it is OK They get the disease when they are out of consecrated ground and when they return there they are already ill. You talked a bog. THat is a perfect place for the demons to lurk and ambush the monks. They might have a grudge to seetle since the abbeuy cut their access to the grotto that you mention
Serf's parma. But 5 for the church and 3 for the other buildings would be OK for me. I am sure there is an official rule in the Divine or the Church about this. Maybe even in the core book.
God is almighty (and quite a jerk, but that is another issue). If you are battling demons and doing this to save the servants of God and your motives are pure-ish, you might find that (inexplicably to you, since the aura still doesn't feel "right" for your powers) you get a BONUS due to the aura, not a malus. God preventing people doing good things is something that has always striken me as quite a debateable issue on Ars aura rules.
Also, remember that (even if you do not want to change the aura) you can take the artillery in the monastery (read: relics, the bible, prayers, holy water...) and use it against the demon. Those are heavy duty weapons against demons.
Or you can go and play with a perfeclty natural phenomenon as you say Maybe even Magic in origin.
Cheers,
Xavi
One thing to keep in mind is that, once you as a player have decided it will be a spirit/demon of disease (or a natural phenomena), it's difficult not to start planning ways for your character to solve the issue.
Which is why it is sometimes better to establish the apparent situation, and let someone else adjuticate the actual causes. That way, as information surface during your investigation, you will be able to think as your character does. That is why I asked for some help for the "Lost Summa" story for Petronius. Using only in-character knowledge to solve a situation is quite difficult, no matter what we say. All of us as players either tend to base our assumptions on knowledge that our characters don't have access to, or compensate the other way and fail to make the links that our characters could/should make in a similar situation.
So my suggestion would be to establish what the situation looks like to an outsider, with a few theories as to what might be causes for it, and let someone else feed you the details as your magus investigates. That will keep the story fresh and challenging for you as a player, providing you with surprises and opportunities for unexpected roleplaying.
Just my thoughts in this.