Project Silver I
The inscriptions sealed off the Mana of the trespassers. The formation strengthened the capabilities of the silver employees. The array formed a magic barrier over the estate, that nullified magic below Juliette's highest circle.
The runes disrupted the skills and spells of the trespassers below Unique grade, or divine category. And the sigils did the opposite for the silver employees, boosting their capabilities greatly.
With this much, even the apprentice butlers and maids could easily take out an adept assassin. And possibly even an advanced assassin sent out as well.
Plus, there was also Sixth or Ninth, who would take shifts to visiting and guarding the Silver household per week.
With their combat prowess, not even grand masters could barge in. Hell, for Sixth, Damien doubted whether even an epic assassin could escape from him, given time.