Request: Idea for Greek made-up artifact

Hey r/mythology! I'm entering a writing contest and I need some help with a part of it. In this story the main character is tried by the Judges of the Dead (Greek mythos: Rhadamnthus, Aeacus, and Minos) for obtaining all human knowledge. Kind of similar to Prometheus' "Theft of Fire" myth. Anyway, I was wondering if there is anything in Greek mythology that could serve as an artifact which holds all knowledge? If not, what would be a good idea for a fake, yet real-sounding artifact of this sort?