Verditius

The Magi of this House depend on magical devices in order to cast their magic. They can only cast Formulaic and Ritual spells through Spell Foci. They cast Spontaneous spells normally. Verditius Magi have achieved significant power by making themselves invaluable to other Magi, creating enchanted items for others. Though Verditius Magi like to pretend they are of lesser power than other Magi, they possess considerable power.

(Copied from Ars Magica 3rd Edition rule book)