After looking at the Concentration table on p82 of ArM5, I have to ask, is there any magi that can cast another spell when concentrating on/maintaining another?
If I read p82 correctly, the mage would need to roll Stamina + Concentration + stress die against an Ease Factor of 15 (not counting wound/fatigue penalties).
My new character effectively has a total of 4, from Stamina +1, Concentration(spell concentration) 2. Thus needing to roll 11+ on a Stress Die to cast a second spell. Doesn't seem likely. Unless I am missing something in the Concentration rules.
My original tactical plan was that my character would cast Rise of the Feathery body to get out of range of certain troubles (wolf packs, charging knights, etc), then rain down destructive spells. Don't think I am going to try that now.
More importantly, every example Hermetic mage I have found the write-up to in books so far, has a STM+Concentration total of 6 or less. So none of them could expect to reliably cast another spell when concentrating on/maintaining another.
There are few spells that have been designed to be maintained while casting another spell (ReVi Maintaining the Demanding Spell, p 162 "a lower roll than normal because this is the way the spell is designed") and their ease factor is lower , but otherwise, as you discovered it is unlikely unless having a highly optimised mage to have a mage maintaining a spell whilst casting another one.
Magic item are much safer for that, they are reliable and more important CANNOT botch. All the situations you described means that the concentration test will be done under stress... unless you are desperate, this is not something you want to do to save your life but it will earn you many brownie points for entertainment value .
That 15 difficulty for casting a spell while maintaining another one is quite high indeed and seems to make your strategy quite hard to accomplish indeed... Vim metamagic spells, as intended to work with another spells, require concentration rolls of 9+, some spells requiring only 6+ if I remember correctly, but that 15 means that casting unrelated ordinary spells at once is pretty hard.
We have a house rule that allows Spell Mastery for concentration, adding your spell mastery score to concentration rolls: something like that could help, but the main solution I see is just getting rid of Concentration: you could invent a Rise of the Feathery Body version of Diameter duration, and then you will only need to concentrate to rise and fall, and keep in place (and keep altitude) if you stop concentrating to cast another spell. Of course you are going to be quite careful with the duration as after 20 rounds the spell will expire and you won't want to be at a high altitude at that moment.
The other solution is to place the concentrating work into something else. Enchant something to make you levitate (or even better to fly, and get some more usefulness) and let the item maintain concentration. Then again you will have to focus on the item to go up and down but if you stop concentrating to cast offensive spells then you will be holding still up in the air.
As a sidenote I would consider casting also an invisibility spell before start levitating, or Winds of Circling Protection or something like that. For my experience a magus hunging from the sky is an irresistible target for anyone with a bow, or stones to throw, or able to breathe fire...
That's already +8, so just barely under a 50-50 chance with a stress die. And this is without major investment. Anyone with Virtues like Great Characteristic, Flawless Magic, and Puissant Concentration could do this more easily. And just a little more investment later in Concentration, Spell Mastery, or improving Stamina would go a long way.
My personal preference is to take Spell Mastery with Imperturbable Casting for a variant of Maintaining the Demanding Spell.
That was the bit I missed from the Concentration rules.
That would make it a lot easier. Pity I missed that in character creation. Still, the SG says we are in still in the period we can tweak our characters, at least the parts that haven't been used in play yet.
So any mage character depending on concentration spells in combat needs to know a reasonably high level Maintaining the Demanding Spell, and be able to cast it.
Hmm,... Would make a Mythic Blood character useful, if their special ability was to cast Maintaining the Demanding Spell ReVi30, at will.
Re-reading the imperturbable casting spell mastery ability from SoS:Societas, makes it sound like it can influence the INT+Concentration roll when applied to Maintaining the Demanding Spell. Good that my character has Flawless Magic.
I know I can't take both.
I was merely speculating about ways to get a character that can cast a high level Maintaining the Demanding Spell (ReVi Gen), to maintain spells of other Forms that require Concentration.
First, it's Stamina+Concentration, as in the rules about concentrating on spells. There was an error with Maintaining the Demanding Spell, fixed in the errata.
Unless you're really weak at ReVi (like Major Magical Deficiency in Rego), you're probably better off with the spell. Especially if you're Mercurian, as are many with Flawless Magic. Just a few points placed into Mastery would give you Adaptive Casting, Imperturbable Casting, and Stalwart Casting. That's +3 to cast it, -3 botch dice when doing so, +3 to Concentration with it, avoiding Fatigue loss, and working with other levels of the same spell. Learn it at a level you can just handle now. Use that as a similar-spell bonus when learning a higher-level version soon. So, sure, maybe you'll start a little lower than the level-30 version you could get, but you'll be better at using it and will eventually be able to upgrade beyond level 30.
I'm not sure where the "other Forms" bit comes in. Maintaining the Demanding Spell works with all Hermetic Forms.
"Especially if you're Mercurian, as are many with Flawless Magic" - seeing as Flawless Magic uses your Major Hermetic Virtue slot, the only way you'll be Mercurian and have access to their Spell Masteries is if you join a Neo-Mercurian mystery cult and get trained up. Obviously people's sagas and house rules may vary, but not everyone's playing in a setting where Mercurian spell masteries appear on every character sheet.
I tend to go for Diameter versions of spells and wait for the spell to wear off after combat. If you are really needing to stop an effect, casting PeVi magic to cancel is straightforward.
You seem to be confusing the Cult of Mercury with the Virtue Mercurian Magic. Being in the Cult of Mercury does not take your Major Hermetic Virtue slot, nor does it require being a member of a particular House. Meanwhile, I'm not referring to special sagas and house rules, but rather to canon statements:
Yes, becoming a Neo-Mercurian is another way to gain access to these, and it can allow you to have both Flawless Magic and Mercurian Magic. So, while sagas and house rules may vary, being a Neo-Mercurian is certainly not the only way to have Flawless Magic and gain access to these Spell Mastery options in canon, and I like to go by canon unless someone's specifically asking about a case that varies from canon.
Perhaps my phrasing was a little clumsy.
I was thinking of Ouroboros's comment that I should also cast Circling Winds of Protection Cr(Re)Au20, which is also a Concentration duration spell, which would require at least a level 20 Maintaining the Demanding Spell.
I am not a practiced veteran of making characters, but it seems to me that it is rather difficult to create a starting character that can cast level 20 spells in both the Form of Auram, and in the Form of Vim. At least my Tremere with Flawless Magic can't.
AFAICS, a mage character depending on D: Conc spells in combat is a rare bird out to make his life unnecessarily complicated. Usually utility, buff and protection spells or effects a magus wishes to keep up in combat do not need to have D: Conc: these are far more useful with D: Diam or D: Sun.
Is there any campaign-specific detail that forces your mage into using D: Conc here? Couldn't you just tweak the spells with this problematic duration, instead of fiddling with extra Arts and extra ReVi spells?
New character, been a long time since I played Ars Magica. Depended upon the main book for spell picks, like every one else in the troupe.
Haven't been in combat yet, but was preparing my tactical ideas when I spotted the issue with Concentration that I had overlooked during character creation. Fortunately I have few Concentration formulaics, but I thought Rise of the Feathery body ReCo10 would be useful in some combat situations, where there was a lack of ranged attacks on the part of the opponents. Now I know otherwise.