[Taqwus]

An additional Communion Fun Fact -- spells which normally would just affect the Communion Master will also affect the slaves.
Summon Earthpower will make ALL the communicants -- all masters share all communicants -- get reinvigoration 4, for instance. Invulnerability will make them all prot-30. Phoenix Pyre will make them battlefield-immortal unless unconscious. And so forth.
Just be careful about overdoing the master/slave ratio -- masters may continue casting spells even when communicants go 200+ fatigue, take damage, and quite possibly die. It's helpful to bring along a nature caster for Relief.