>Then I'll amend my statement to say that an astral 6 void lord with a starshine skullcap and a ring of sorcery can cast master enslave.
Sorry, try again.
Such a mage would have the skill but would not be able to eat the fatigue... all 800 points worth. Since the spell needs 8 gems and the mage is skill-8 you have no way to lessen the problem.
You either need more skill or need a communion.
Communion is the most common way to pull of Master Enslave, as the fatigue cost is staggering.