The Magi wish to cast a level 50 ritual that a Mercurian Magus has invented. As a Mercurian he knows a Wizard's Communion at the level of the highest Ritual he can cast.
As WC needs to be sun duration to actually work I ruled that this was to mean "at the level of the spell gained +2 for Sun", but this has pushed it over the 50 level such that now Wizard's Communion is now over 50.
As a formulaic spell, WC must now be a ritual, but WC is a bit weird as it never needs to be 'cast' just known. Am I missing something or is WC now effectively capped at 40?
Yes, if you are doing long spell-casting (such as a ritual), you need a sun duration WC, which would drop the maximum effective level of it to around lvl 35 to avoid it being a ritual. But that isn't really a problem, as they only really need to know Sun duration WC at level 20. Anything higher than that is a bonus.
Going by the guidelines in the core book
We want to cast our "Aegis of the Hearth" lvl 30 with as much penetration as possible. We have 4 magi in our covenant, each knows WC at level 30 (D: Sun), which grants 20 towards a WC.
The magus who knows the spell and has the best ReVi score leads the ritual, The other 3 join in the WC and we have a total of 80, 20 more than they needed to cast the lvl 30 spell.
The lead magus has a ReVi casting score of 43 and he rolls 4. The effective level of the spell is 30/4 = 8. 47-8 = 39 Penetration for the aegis.
We want to cast our "Aegis of the Hearth" lvl 30 with as much penetration as possible. We have 6 magi in our covenant, each knows WC at level 20 (D: Sun), which grants 10 towards a WC.
The magus who knows the spell and has the best ReVi score leads the ritual, The other 5 join in the WC and they have a total WC of 60, just what they need to cast the lvl 30 spell.
The lead magus has a ReVi casting score of 43 and he rolls 4. The effective level of the spell is 30/6 = 5. 47-5 = 42 Penetration for the aegis.
As you can see, as long as you have enough magi to provide the magic, it doesn't matter how low they know WC at, as long as it is higher than 10 (or 20 for D:Sun).
Not sure I agree with the interpretation that WC doesn't need to be cast. It's a spell, there are rules for casting spells. Roll for WC casting, then add up the levels of the various versions of WC.
But yes, with respect to rituals and D: sun variants of Wizard's Communion, it's effectively capped at 40. But let's not forget that WC can be used for formulaic spells, too. And it makes penetration a slam dunk...
No. "Communion is a remnant of Mercurian rituals, so ... it does not perfectly fit into guidelines of Hermetic theory".
Then the level is simply described as "Base effect", so Range, Target or Duration modifier.
The fact that we are considering a Communion with Sun duration might not even be possible (even if everybody agrees to HR that) - which of course is a problem for all rituals.
That's true for low level rituals, but we're trying to cast level 60 rituals here. That means we need 120 levels of WC, spread between 5 magi, so everyone needs to know a level 35 sun duration communion. Even higher level rituals will increase the amount of WC required, though I'm not sure how often those come up. Level 60 covers the +1 to a stat, to a maximum of +5, which I assume comes up somewhat often.
It's still just as true in your case. Brutus states that "as long as you have enough magi to provide the magic, it doesn't matter how low they know WC at" (emphasis mine). In your example, what has changed is that you do not have enough magi.
An interesting question has occurred to me. WC doesn't really function as a spell itself, it is just a way for people to combine their magical power. It does not depend on the art scores of anyone except the lead magus. They don't need to know it at the same level, or contribute equally. So, is it subject to the same rules about maximum level?
If it reaches level 50, does it need to become a ritual?
Thanks Tellus, you saved me the trouble. I will add that there is nothing here saying that the people have to have high art scores to cast WC. You can always teach WC to a few apprentices and get them to join in. As long as they have a ReVi lab-total >= 20 they can learn it. ArM5 p95 "Learning Spells from a Teacher"
You could always make a minor story about borrowing an extra magus or two who will help with the ritual.
Considering that there is (almost ) an agreement that Aegis needs to Penetrate to affect spells it is blocking/countering, it is reasonable to assume that most mage spent once a season to learn Communion at level 20, with a Sun duration, if not only for the Aegis.
I would not be surprised that either it is an common understanding within the Order that it is simple courtesy to know it once you are 10-20 years out of gauntlet (with a 5 in both MuVi, that you will need sooner or later to take an apprentice), and some covenant might even have it written in the charter the need to know it to efficiently contribute during the Aegis ceremony.
I believe in earlier version every participants needed to roll a stress die to contribute to the spell, but fortunately it is no more the case...
Does Day of Communion explicitly state that there is no spell casting roll necessary?
The language of Wizard's Communion is ambiguous, in that it says magi in the gathering who know the spell add all of the levels at which they know the spell, but it doesn't explicitly state that you don't roll for casting the spell. Indeed, if a magus knows a 20th level, 30th level and 40th level, couldn't they add all those levels to the final level of the spell? Why not?
No, it's far more reasonable, unless it's explicit in Through the Aegis, and I don't have it handy, that Wizard's Communion and it's variants are cast as normal spells. The levels of the cast spell are then combined to determine the Communion total and then used to aid in the casting of the high level spell.
If it is truly the case that this is a spell that is never cast, using an ability (accelerated or not) to determine how magi combine their powers, instead of a spell that isn't a spell.
Good observation, and I agree especially for cannon characters.
A counterpoint though is that it's been raised more often recently in the forums and in games than say 5 years ago or more, perhaps there is a shift in thinking toward building optimal characters and collaboration rather than concepts for individual characters. Imho WC or the ritual variant is a very desirable spell, far more than I'd realised before. Perhaps it's just me.