Hassad, from Ultima V: Lazarus
Hassad had fled Skara Brae when Blackthorn's men under the dark mage Flain moved into the city, hiding on the far-away island of New Magincia under the care of the merchant Kaiko. However, one day the Shadowlords noticed him and hauled him to Blackthorn's palace. As prisoner, he was regularly questioned by the dark king in order to reveal the Word of Power to the dungeon Hythloth, but he refused to reveal it.
After having heard the story from Kaiko in Ultima V, the Avatar finally found Hassad in the dungeon of the castle. Hassad was very careful with what he would say, and only after revealing that the Avatar knew Kaiko and telling Hasad the password of the Resistance, did he reveal the word.
However, he didn't want to be freed, seeing as that would be pointless at the moment. It is most likely that Lord British freed him after sending Blackthorn through the red gate.