The book had an immensely important role in Ultima VI. Iolo snatched it from the hands of the dead Gargoyle priest while rescuing the Avatar from being sacrificed. The Avatar showed it to Mariah after getting a clue from Nystul. She was able to decipher the title, but she needed the Silver Tablet to translate it completely. The Avatar, now knowing the motivations of the Gargoyles, tried everything from that point to save the Gargoyles from destruction. The 'sacrifice' the prophecy spoke of, in the end, was the Avatar's sacrifice of the Codex of Ultimate Wisdom to bring peace.