Rune Inscribed Skull

The practice of making an arcane focus from
the skull of another magic user is among the most heinous in the eyes of the mages of the "civilized" world. However no one denies the potential power of such an artifact.
This skull acts as both an arcane focus and a spellbook. Sometimes it seems to be looking
at you, sometimes you imagine you hear the whispered voice of a long-lost friend.