Tegana was the main antagonist in the first season seven-part Doctor Who story "Marco Polo".
He was portrayed by Derren Nesbitt, who also portrayed Major Von Hapen in Where Eagles Dare.
Tegana was a Mongol warlord travelling with Marco Polo's caravan in 13th century Cathay. Ostensibly, he was there as an emissary from his ruler Noghai. In reality, he was on a mission to assassinate Kublai Khan, after which Noghai's forces would invade his territory. When the party encountered the Doctor, his granddaughter Susan and companions Ian and Barbara, Tegana tried to have them killed immediately but Marco intervened and invited them to join their party. Both Marco and Tegana were intrigued by the TARDIS, which they dubbed a "flying caravan". Marco insisted on keeping it for the Khan while Tegana plotted to steal it for Noghai.
Tegana first attempted to dispose of the rest of his party by destroying their water supply as they crossed the desert. He rode on alone to an oasis to fetch water, but once there he made no attempt to return to the others, leaving them to die of thirst. They survived by drinking condensation that had formed inside the TARDIS and Tegana claimed he had been unable to leave the oasis because there were bandits nearby. In fact, Tegana himself was in contact with a group of bandits led by Acomat, who he had hired to attack the caravan if necessary. He allowed them to capture Barbara when he followed her to a meeting, but when the Doctor, Marco and the others arrived, Tegana killed her guard himself, maintaining his innocent façade with Marco even though the Doctor and his friends were now fully aware of his evil nature.
Tegana prepared for the bandits' attack by killing the lookout but lost the element of surprise when the Doctor and Ian found him dead and alerted Marco. The bandits attacked without Tegana's signal only to find the party ready for them, and Tegana killed Acomat himself to stop him giving him away. He managed to thwart the TARDIS crew's attempt to sneak away to their ship by grabbing Susan before she could join the others, forcing the Doctor to surrender the TARDIS key to Marco. When Ian went after Ping-Cho, a girl who had run away from an arranged marriage, Tegana convinced Marco to let him go after them, arguing that Ian might not bring her back. He tried to use the opportunity to kill Ian, but when the Khan's soldiers arrived, he settled for having them arrest Ian instead.
Once at Peking, Tegana quickly began causing a rift between Marco and Kublai Khan, accusing Marco of favouring the Doctor and the others and allowing them to flaunt the Khan's laws. The Doctor and Ian finally managed to convince Marco of Tegana's plan. Tegana killed the Khan's vizier, but before he could kill the Khan himself, Marco arrived and he and Tegana fought. Tegana was defeated and, surrounded by the Khan's soldiers, ran himself through with his own sword rather than be taken prisoner.