[apoger]

>Remember also that even an astral 1 mage can cast master enslave if he has a full load of gems.

Um...no.

Sadly it looks like gem usage is not explained well (at all) in the new rule book. At least I can't find it.

In Dom1 a mage can only spend one gem per level of skill. I appears that this holds true in Dom2 as well.

You need very potent mages to cast the serious spells. Beyond even the skill and gems you must account for fatigue from the spell. If a spell will take you over 200 fatigue it will not cast, since this would endanger the mages health.