Shak, from Ultima Underworld
When the Avatar first found him in his hidden workshop on the second level of the Abyss, Shak offered his services of repairing and identifying items for the right price in gold. He also told the Avatar about the fantastic sword Caliburn, the sword of Justice.
This proved to be important, as the Avatar later found Caliburn broken into two pieces, and it took Shak's experience (and lots of money) to forge a functional sword. Shak was also delighted to see the Shield of Valor, if the Avatar had acquired it and chose to show it to Shak. Later, he was likely rescued by Garamon, when the volcano erupted.