Team players.

Ok Rob, based on your advice, I worked this out:

Some ritual spells may be cast by one or more shamans casting in unison. Each spell has a 'multiple caster' rating. 1-3 indicates that one two or three may cast the spell.

In this case, each shaman can contribute one or more spell points, depending on the spell. For each shaman casting, the resist modifier for the spell is multiplied. Thus, whereas a 2nd circle Fear spell has a resist modifier of willpower +2, if three shamans cast it, the resist modifier would be +6.

Also, there are going to be some spells rated like 3-6, meaning at least 3 shamans must cast it together. -These could be much more powerful. You might get a 8th circle effect with a 5th circle spell if three 5th circle shamans were required to cast it.

I dig this shit. We've got your chanting monks.

BTW, the working spheres for ritual spell points are Blood, Dream, Gaea and Stitch.