Tegana posed as a peace emissary from Noghai to Kublai Khan in 1289 and travelled with Marco Polo's caravan. In truth, he planned to assassinate the Khan. When the First Doctor, Susan Foreman, Ian Chesterton and Barbara Wright joined the group, Tegana was suspicious of them and wanted to destroy them as evil spirits. However, Polo stopped him.
During their travels, Tegana tried to make Polo suspicious of the Doctor's group. At the same time, however, Tegana was making arrangements for a group of bandits to attack Polo's camp. Each time, he was defeated, but Polo never suspected him and refused to believe Ping-Cho and Susan when they accused him of helping to kidnap Barbara.
Tegana also tried to steal the TARDIS for Noghai, but it was eventually brought to Peking. In Peking, Tegana attempted to kill the Khan, but Polo stopped him and they fought. Polo defeated him, after which he committed suicide. (TV: Marco Polo)
The Doctor said that Tegana had "bloodthirsty habits". He enjoyed chess, which he called fascinating, and Polo described him as being no fool and being capable of looking after himself. Susan was of the belief that he was a man that would not take a walk unless it were for a purpose. (TV: Marco Polo)