My troupe has only just discovered the delights and possibilities inherent in the Wizard's Communion.
For those who haven't checked this out as yet (and if not, why not), the Wizard's Communion allows multiple magi to cooperate in casting a given formulaic or ritual spell. One magus takes responsibility for actually "casting" the spell, but the spell's effective level is divided by the number of magi taking part in the communion. So, a level 50 spell cast by a communion of 5 magi means an effective spell level of just 10. This allows two things. Firstly, potentially very difficult spells are made achievable. And secondly, the Penetration achievable improves by virtue of having a lower effective target level.
This is all good stuff so far. You can see the potential already. But in planning what we were going to do, we had to read the spell text very carefully. As a spell that's been adapted from Mercurian ritual, there's no direct easy fit into Hermetic standards. Importantly, there's no mention of needing to cast the Wizard's Communion. Only the level at which it is known is important (all the magi present sum the level they know Wizard's Communion at and so long as the total is twice the level of the target spell they can cooperate).
So we understand the mechanics, but it does throw up some questions.
Although Wizard's Communion doesn't need to be "cast", do you enforce any preparation time before the effects of the Communion are granted?
Given that there are no casting rolls for Wizard's Communion, how do you have it interact with mastered multiple castings?
Once the Communion is joined, can all magi present cast their spells round after round with benefit?
The four magi are in four different places in round one. For their action in round one they all move to a given point such that they're in the same place at the beginning of round two. When round two starts, can the lead magus cast a spell aided by the Wizard's Communion? Looking at the rules as written, I don't think there's anything to prevent this. I'm not sure I like it from a flavour perspective. It feels a little too power rangers to me.
The magus with Demon's Eternal Oblivion has it mastered and able to cast three copies at once. He's working in Communion with another magus. Are all three castings affected by the Communion? I'd say so. Communion does not need to be cast, and the other magus is feeding power into the process throughout the round.
A group of four magi join in Communion. Can they each cast a spell, aided by the Communion, in that round? I'd say not, although I'm not sure that's supported by the RAW. I see the act of Communion, culminating in the target spell casting, as being everyone's action for that round. But can a different magus cast a different spell in each subsequent round? If the consensus is that no preparation is required, then yes. If the magi just have to "touch power rings" or some such act, then the Communion is open for all to take advantage of. But if the gathering of the Communion is specific to the target spell, then it needs to be broken and new preparations need to take place.
This is a powerful effect, but I think it needs to be handled right in open play so I'm looking for suggestions or rulings that you guys have made.