Dojjen

Dojjen was a Manussan historian and Ambril's predecessor as Director of Historical Research.

Biography
Dojjen believed that the Mara had not been destroyed and would someday return, which caused him to go to the desert to learn the rituals needed to defeat it. He later taught them to the Fifth Doctor. (TV: Snakedance)

The Doctor later mentioned a desire to catch up with Dojjen. (AUDIO: The Cradle of the Snake)