Trying desperately to divide up the OOC and Table Talk threads....
So what ends up happening with Ogmios's Saddle? I have a season dedicated to adding enchantments to it, but cannot find the final enchantment formula that we agreed on.
I think, last I remember, we were going to put in an effect that would turn a horse into a flying steel pegasus. In the 1222-1227 OOC and the Viscaria Verditii threads.
So the formula is:
MuAn(ReTe), Base 4 (as per Beast of Outlandish Size), +1 Size +2 Sun (+2lvl 3uses/day + 3lvl linked trigger)
(+1 Rego requisite + 1 Terram Requisite) = MuAn(ReTe) 30 to make it a Giant Flying Courser with bones/wings of steel.
Don't we need +1 Touch in there somewhere?
That would make sense, wouldn't it?
Maybe we only need +1 for the Requisites?
I'm looking at the Requisites rules on pp. 114-115, and I honestly don't think that the requisites require an additional magnitude, since you need the requisites for the spell to work. If the requisite "simply allows the spell to have its effect," they "do no tadd to the spell level, as the difficulty of doing such a thing is already accounted for in the guidelines." (p. 114, second paragraph under "Requisites".)
IS it at all animal or just animal shaped?
IMO, Animal isn't even a necessary requisite... Am I missing something?
If I'm remembering right, what the new spell does is takes the horse that's created with the Saddle (The Wizard's Mount) and transform it into a flying steel pegasus. So it would need the Terram to turn it into steel, and the Rego requisite for it to be able to move and fly.
Nevermind...carry on. 
Makes it bigger, armored, and flying.
Did we ever look to see what the levels would be for creo?
You mean to make a new horse, as opposed to transforming the one that's being created? Don't think so. If we did, it was early on.
The base Wizard's Mount has a Size+1 built into it, and base individual is up to a pony (Size+1), which, by the collossal stupidity of the size system, does mean that it can create a horse up to size+4, IIRC.
It doesn't and won't, due to the parameters of the spell. We could do the same spell, to do a larger effect.
If making a bigger horse that is within the capacity of the original spell counts as a "superficial" change, then we could get away with doing a MuVi (Base 15 + 1 Touch, +2 Sun + 2 3use/day +3 trigger = ) 35, which would be easier for Viscaria to do, but the MuAn(ReTe) is within her grasp, so why bother changing plans? The pegasuarus is cooler.
Adding a size increment, IMO, is beyond the scope of a superficial change.
Not so ridiculous. A heavy warhorse is Size +3, and a ten-fold increase of Size +1 puts it right at Size +4. Granted, most wizards wouldn't want a horse the size of an elephant, but you can always make it smaller than the maximum size. I'm thinking Fiona would want one on the upper end of "heavy war horse." Say, roughly 2500 pounds/1150 kg. Which is still in lower end of +4.
I think changing the size of the target is a "superficial" change, as long as it doesn't change the Size. Creating a horse that's 2500 pounds or 4500 is superficial, since they're both Size +4. In my opinion.
I agree with this. If it's within the guidelines of the original spell, adjusting the size is only a superficial change.
So, do you want it to be MuVi 35 for a bigger horse, or MuAn(ReTe) 30 for the pegasaurus?
Does the pegasaurus already have the +1 for Size modifier that the Wizard's Mount has? If so, that will be fine (that puts it at up to a +4, which should be big enough. It would need to be a +4 Size to easily carry Fiona and any armor and weaponry).
Yes, there is a size mod on both spells.
Yes we do, if the item is to change a horse it is touching.
And no, the base ain't 4 
You gotta use the highest base needed.
You're changing a horse into Metal. That's not base 4.
That's not even base 5 (Change an animal into a different animal. Change an animal in a minor way so that it is no longer natural).
Based on the Muto Corpus spells that change you into an element (cloak of mist and the spell to change into water), you need Base 15 (Change an animal in a major unnatural way. Change an animal into a non-living item). All these spells use the base 30, for changing into an insubstantial object, which is only 5 higher than changing into an inanimate item, which you'd use to turn a human into stone, or metal.
Which is exactly what you're doing here, essentially (turn a horse into metal), save that you're also giving it the ability to move. This is a major change, quite on par with Steed of Vengeance.
"Beast of Outlansdish size" is just an added effect on top of that, nowhere near as hard as changing it into metal . Compare what you want to do with "Steed of Vengeance", which uses base 15 for "major unnatural way". Does this seems any less major or unnatural?
You would probably have a waaaaay easier time creating a metal horse directly.
??? Why Muto Vim???
Changing dirt into an animal is MuTe base 5. Changing metal into an animal is Base 15. The muto guidelines for Animal are generally easier than for Corpus.
Checking the rest of the MuAn guidelines, it seems that what we want to do is actually Base 25, plus requisites. So, I'd need a lab text to do anything on that scale.
Now, I could keep it as MuAn Base 4, and ditch all the other ReTe fancy stuff, which would leave it as simply a larger horse. Or I could MuVi to change the spell so it makes a bigger horse, saving you a command word. Or, possibly, I could instill a second Wizard's Mount spell...but that would definitely require a lab text -- we have the lab text for Wizard's Mount (the spell), but even with the new house rule, I don't think that helps me unless I've actually learned the spell.
MuVi, to change the spell superficially so that it summons a larger horse within the parameters of the spell already built in.