The Power of Kroll
Varlik was a Swampie chief on Delta III. He helped Rohm-Dutt kidnap Romana I.
After Kroll killed Mensch, Varlik began to doubt Kroll. Ranquin later suspected him of freeing the Fourth Doctor, Romana and Rohm-Dutt, as Varlik had thought they should die from the first of the Seven Holy Rituals, not the seventh. He, along with the other Swampies, took part in the attack on the methane refinery. (The Power of Kroll)