"Yes, but we were talking about what I ought to do to pay her back for making a transformation pendant for Theraphosa. The more we talk about it, the less this sounds like the project I should do in exchange for it. Cygna should modify the saddle herself, since transformations are her specialty. I suspect she should conceive of an enchantment which lies within my area of expertise and outside her own for her payment. Perhaps a combat spell? A Ring of Crystal Darts with....over 8 magnitudes of penetration?" (ooc: Penetration 44) "Or a defensive spell? Something that conjures a shield wall?"
Maybe...
If there's some space left, you could enchant the saddle so that it conjures a magical armor for her horse. Something that couldn't be done by mundane means. Tough, flexible, and lightweight, so as not to impede its movement.
So, looking back at Theraphosa's doohickey that Fiona's making in the summer of 1226. Did we ever decide whether we wanted it Concentration or Sun? And is Theraphosa wanting to help in the lab? (basically, if Thera helps, then we can do the Concentration duration so she can change basically whenever she wants, and we don't have to experiment)
And I'm fine with Fiona's payment being a "solid 'you owe me'" down the road.
Sure! She can help Fiona in the lab. Though if you offer to experiment, she'll be very interested -- Viscaria rarely experiments at all.
Okay, so shall we go with the twelve uses a day, concentration duration, with the item maintaining concentration, and only usable by Theraphosa, then? When I ran the numbers before, I came up with a Spell Level of 20, and an Effect Level of 40.
Using a magnetite piece of jewelry brings us to a Lab Total of 76 without experimenting. Experimenting increases Fiona's and Sheelagh's help by 6, which takes us to 82 + die roll of 9 = 91. Done.
Now for the icky part. The Extraordinary Results chart. Die roll of 6 shows Side Effect. Die roll of 9 comes up with "The spell has a major side benefit. For example, a spell that transforms you into a wolf also lets you speak to all beasts while a wolf." This could be interesting.
~dances~ Genius! Pure Genius! I can't wait to find out what the side effect is.
Was this the base MuAn/Co spell that gave her a basic human form, or the one that kept her multiple arms, spinneret, etc?
Unfortunately, it was "just" the base MuAn/Co with the basic human form. Unless, by some stroke of miraculous luck, that winds up being the "major side benefit". anime puppy eyes
If it is a hybrid animal/human creation, Fiona might want to dive into the research rules and try to stabilize that effect. Doing that to grogs would make for some pretty nasty soldiers.
There is no stabilizing of an effect when experimentation is used outside of Original Research.
For a Major Side Benefit, I don't think having multiple arms would be a great boon, since it would defeat the main purpose of the spell, which is to allow teraphosa to pass as human in the first place.
If it was a Sun Duration spell, I'd have let her end it at will.
For an item... This is trickier. What about saying that she can select a different appearance with each casting, between size -1 and +1? Given a good finesse roll, this would allow her to impersonate people, hide in a crowd, in short, be a more efficient hunter.
Oh, and what about making Teraphosa our Spymistress?
I think you would need to master the spell to get Harrnessed to you can end the spell at will.
I'm pretty sure that I already suggested making her the Spymistress.
Allowing her to change appearances would be cool, but I think that counts as an expansion of the base effect, not a major beneficial side effect. It should be a power orthagonal to the intended power. So, by that logic, even if it allowed her multiple sizes/shapes AND let her keep her physical skills regardless of form, it still isn't the same as a "major side effect."
Dude, you know that Viscaria brought a copy of Rarefy Earth Elemental and has put it in the library, right? Elemental control is a back burner project for her as well -- especially given how Rego-focused we're all going to become soon.
You're perfectly right, but as we're talking about experimentation and a major side benefit, it wouldn't strike me as unreasonable to have the spell be "naturally" harnessed.
Anyway, amul's objection is sound, too.
Hum...
What about another hidden Corpus effect? Like, while in human form, she's under an Endurance of the Berserkers effect?
Or if we're to have it totally disconnected from the base effect, what about an Aura of Beguiling Appearance?
...
...
Going back to the Magus planner... No no no, it's all impossible to change! I need my Ice spells, I need the Rego and the Vim for the WC and the Aegis... Ah!!! 1224!!! There are just 2 seasons I can change!!! And easily, nothing depends on them 
Holy thanks!
Great news: Given vis, we can have some Earth Elementals by 1227 
Also good options. Additional suggestions: Gift of Frog Legs, an additional sense or a greatly improved traditional sense.
Um...have you read the Taming and Training rules in RoP:M? If I understand the rules correctly (and am remembering them correctly -- I'm away from my books), once rarefied, you then have to tame the elemental (takes a season) with a ReFo (ReTe) lab activity and then spend a season per command training it to do things. Until then, you're going to need to keep it in a circle or something.
Note that we do not actually have a source of Terram vis (which Viscaria gets around by BEING a source of Terram vis). Although we seem to have nearly a queen of Creo, so go hog wild, I say.
Also, given her Imbued With Spirit of Terram, that earth elemental is either going to cower in terror or go beserk every time she runs into it. Which is fine by her, cuz she memorized Command the Living Stone before she ended her apprenticeship (gee, thanks for looking out, pater). And frankly, the visual of an earth elemental cowering before a Size -2 sari-clad kawaii girl is the entire reason that I want earth elementals in my covenant.
Please note that while Viscaria will be extremely pouty about someone else learning to rarefy earth elementals before her, the player is very pleased by this turn of events.
As I put together the letters ( 8 more to go) for the various Mercere Mages ( from a list provided by JL) I noticed that they are not as tightly grouped skill-wise as one would think. Since the Mercere House is a True Legacy all of the Magi would have to be apprenticed by another so they would have very similar skills ( as we have noticed from Apprentices...the book). I was thinking some editing would have to happen to build a family tree as it were.
Some editing will have to happen so some will fit.
One example:
Lykos is the the Thebes Tribunal. There is one other Gifted Mercere there named Hypatia. So we could assume that Lykos filius Hypatia but not so fast my friend 
Hypatia is Mercurian and Lykos is Mutantis so they would seem not to fit well. In steps Vincentius who is in Loch Leglean but recently was in Levant. He is a martial mage as well and a Mutantis and Mercurian ( not sure you can have both virtues. Will have to research). I think it would be Lykos filius Vincentius.
Some match up well and others will need tweaking. But with only 14 magi in the House, not an overwhelming task.
Korvin is filius Alessandro, who is an old codger who will have quite a few 'children'.
With Arya no longer in the saga, you don't have to feel yourself constrained by anything she had created/added as far as the Magical Mercere go. Keep what you like, jettison what you don't, or create it all from scratch.
There are some inconsistencies with the HoH:TL text. I have trouble understanding how the House can be as diverse as it is with so few magi...
HoH:TL has most of the Mercere Magi in the Rome, Greater Alps with some in the Rhine, and Thebes I do not mind her list as it almost makes sense to spread them out to support the Redcaps. On the other hand, most, if not all of the RedCaps would be able to get to Harco is they needed a LR or some item.
It is good to have a list but it will be edited. I will move some of the outliers to the Greater alps and Rome Tribunals. Like Boris at Fengheld ( who just got a letter). Horst is already living in Fengheld( although a non-magical Redcap) and Xavier is at Durenmar ( as per HoH:S). Lykos will be coming to the Greater Alps as will Attravere ( who has also gotten a letter). I think Harco will have at least one Mage in residence. Attravere makes sense because he is a transportation expert and he is Italian.
Two others that are coming closer to Harco will be Beatriz ( from Novgorod) and Silvana from Hibernia.
I'll throw it on the OP wiki when I'm done.
With the travel focus of the House and the mundane power base, it makes sense that they'd keep the magi moving around the globe. No sense in letting a magi hang out near his parens. But with only 14 magi, you really have to wonder about where they get all those magical devices and longevity potions from.
I bet most of the Magical Mercere have a Verditus covenant-mate with a huge hubris score.
Also: no wonder Mercere Portals cost so much!
It would be great to have a Merrinta teach a Mercere apprentice Targets/Range of Road/roadway
But why have a Magi traveling all the time when the Redcaps can just come to them. Would you like moving your lab every seven years?