Theodore Caedmonessunu is a mechant in Eoforwic (York). From the spawning in the area, go north and cross the bridge and you will find him northwest of the bridge. The trader Berthgyth Cenredesdohtor is west of him.
Depending on your reputation he is willing trade the following items. With neutral reputation, he will sell them at disagreeable rates, while being idolized, it will be generous.