Naxatilor, from Ultima VI
He led the seers of the land, and it was he who originally located the Codex of Ultimate Wisdom in the Ethereal Void and found a way to bring it into the world for his race to use. Naxatilor also created the Vortex Cube. In Ultima VI, he advised the Avatar that the prophecy in the Book of Prophecies could be averted if the Codex was returned to the Void so that both humans and gargoyles could benefit from it, and instructed the Avatar on how to proceed.
His final fate is unclear and he wasn't heard of again.