Theol Willoughby was a young boy on Trenzalore. He helped the Eleventh Doctor battle a Krynoid invasion during the Siege of Trenzalore. After the Krynoid's defeat, Theol made a special walking stick for the Doctor out of the Krynoid in memory of the farmer Pieter, who had been taken over by the Krynoid. (PROSE: An Apple a Day...)
Multi-adventures reference the rare instance when a companion is shown or stated to have multiple adventures with the Doctor but only appears in a single story.
If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.