Landon, from Ultima V: Lazarus
After following the trail from Terrance in Britain to Chamfort in Yew, the Avatar with the latter's help managed to enter the sewers beneath Yew. There he found Landon, who after getting the correct password from the hero, officially welcomed the Avatar in the Resistance, offering information to help with the quest, namely saying where the Crown was, suggesting to see Sir Simon in Bordermarch for further help.
However, other than that, he didn't offer any further help to the Avatar.
Ultima V: Lazarus Edit
In Ultima V: Lazarus, Landon's role is expanded. He now gives numerous quests to the Avatar and also comments on the various actions taken to weaken Blackthorn's regime, each linked with an experience and karma gain.
The Ultima 6 Project Edit
Interestingly, in The Ultima 6 Project, Landon's journal can be found, long after he's gone.