A Grimoire is a multiple-entry Physical [Spell Matrix] which is specially designed to easily convey the information of how to cast its spells.  In addition, a Grimoire is *always* a [Pattern Item] for the magician who owns it, with a thread tied to his memory. Consider this as an explanation for why magicians never need to memorize their spells --- the Grimoire locks the information into his head.

Magicians can tie threads to the captured Grimoires of others.  This allows it to be used as a Physical [Spell Matrix], but does not provide the memory-enhancing effect of a personal, [Pattern Item] Grimoire.