[Taqwus]

Don't forget that extra gems/slaves can be consumed to reduce the fatigue caused by casting spells (but not the encumberance-based fatigue).
In addition, fire spells incur more fatigue during rain.
Once fatigue hits 100, 5 fatigue is recovered per turn -- but only until fatigue drops below 100, at which point the caster is barely conscious. The next spell will probably knock him out again. Item (e.g. Boots of the Messenger, Amulet of Resillience) / spell (e.g. Summon Earthpower) / blessing (earth 4+) reinvigoration takes place even when conscious 'tho. Item negative reinvigoration (flame helmet) takes place constantly as well.
Primary spell path = first path listed with spell. Blood is always primary if present.
Communicants keep absorbing fatigue even when unconscious. A long battle or one with too many communion/sabbath masters can kill all your communicant/sabbath slaves.