[Gateway103]

Communion does work in raising skill levels, it is just not displayed. You can easily test this with Pythium default theme with spells a few level beyond your Arch Thurgs's path.

Regarding fatique, this is how I understand it:
While the increase in path does reduce casting fatique, you must note that each slave also get charged their basic spell casting encumberance when the master casts a spell in addition to the fatique distributed from the actual spell. So if the fatique from the spell, after skill reduction, is say 40 and there are 4 slaves, each slave would get 10 + casting encumberance per casting of this spell.

This means, casting multiple low fatique spells with masters would apear to worn the slaves out quicker than expected, due to accumulating encumberance fatiques. Oh, and Masters also get their basic spell casting encumberance fatique per casting, but none from the actual spell fatique, which is distributed among the slaves.

Hope I am remembering correctly.

-Gateway103