Ranquin

Ranquin was the leader of the Swampies on Delta III. They turned to him after their forced exile from Delta Magna. He firmly believed that Kroll was a god, and worshipped him as such. In this respect, he was also the religious leader of the Swampies.

In the swamps
Some humans began refining various elements on Delta III, which they had not known of when the Swampies were transferred there. The workers oppressed the Swampies and forced them into the swamps. Over time, the Swampies came to worship Kroll, which Ranquin proclaimed to be their god.

Against the refinery
Ranquin purchased guns from Rohm-Dutt for an attack on the methane refinery. The guns turned out to be duds, as Rohm-Dutt was secretly working for the refinery. Ranquin ordered the sacrifice of Rohm-Dutt, the Fourth Doctor and Romana I to please Kroll. They managed to escape. As the Swampies pursued them, Kroll appeared and attacked the Swampies. This made many Swampies doubt Kroll as their god. Ranquin, however, was firm in his belief, deciding that it was a test of faith.

He led a raid on the refinery and tried to contact Kroll, who was also attacking the installation. A tentacle of Kroll burst through a pipe and Ranquin approached it. Kroll then grabbed Ranquin after being attracted to the Swampie leader's talk and killed him. (TV: The Power of Kroll)

Behind the scenes
Frederick Jaeger, T. P. McKenna and Gary Watson were offered to the role before John Abineri was cast.