Mages may work together towards a common goal for spellcasting.
This is handled like any other action where characters combine their efforts.
The mages involved in the spellcasting must all have at least one dot in the Arcanum required to cast the spell, while the leader must have the required Arcanum rating to cast it himself.
If the leader knows the spell as a Praxis or Rote, the spell gains the benefits of those methods.
Any secondary caster who meets the Arcanum requirements rolls her own casting and adds her successes as bonus dice to the leader.
If a secondary caster does not meet the Arcanum requirements, she rolls Gnosis (no Arcanum) with a –3 penalty, and provides any successes as bonus dice to the leader.
Each participant must roll for Paradox separately; if any one of the casters releases a Paradox instead of containing it, it affects the entire spell.
Mages without the Arcanum used at all, Sleepwalkers, and Proximi may also assist in the casting, but do not roll. Instead, the casters may use their participation in the ritual as an environment Yantra.