Tendrak

A Tendrak was one of the many creatures captured by the Zygon warlords, Anktra and Kestral. They planned to carry out a traditional duel on the planet Shontaa, involving fighting to the death using this variety of host bodies. This duel was observed, however, by the Fourth Doctor and Leela, who were on Shontaa for a picnic. The Doctor, realising that the Zygons had the hosts they were mimicking locked up, found the Zygon ship and freed the prisoners. (DWY: Rest and Re-Creation)