Tekazoid cave-beast

A Tekazoid cave-beast was one of the many creatures captured by the Zygon warlords, Anktra and Kestral, who 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 must have the hosts they are mimicking locked up, located the Zygon ship and freed the prisoners. (DWY: Rest and Re-Creation)