I did not assume that he took Penetration as his first special ability.
Magic Resistance looks much better, if the the King of the Mountain wants to return the favour. 
ArM5 p.86: Hermetic magi can study Formulaic and Ritual spells that they know in more detail.
The caster does not know the spell, therefore no mastery.
Well, I had to save casting tablets for my saga too. 
Regard,
adumbratus