Lon

Lon was a Manussan was the heir to the title of "Federator" when he encountered the Fifth Doctor, Tegan and Nyssa. His mother, Tanha, struggled to make him understand the weight of responsibility attached to being, effectively, a prince, but he showed little interest in his destiny. Worse, he showed no interest in his people's history, despite repeated attempts by Ambril, a kind of "court historian", to get him to investigate local sacred caves.

However, when Tegan offered to meet him privately, his ostensible boredom with life temporarily abated. He believed Tegan was making a romantic overture, but as she was under the control of the Mara, she had distinctly different plans. Taking his hand in hers, she brought him under the control of the Mara as well. Lon then began to use his power as "deputy Federator" for the Mara's benefit, a situation that obtained until the Doctor eventually destroyed the Mara. (DW: Snakedance)