Tunar and his crew of Fishmen were seeking out the giant Ramlak beast across the Sand Sea, which was responsible for drinking all of the water in their oasis habitat. During their hunt, they managed to capture Lion-O and his band of Thundercats who had just begun their journey to find the Book of Omens. Tunar was prepared to let his crew feast on the Cats, but the ship was suddenly attacked by the Ramlak and the Thundercats helped the crew drive it off. Impressed by their fighting abilities, Tunar allowed the Thundercats to remain aboard to help him in his quest to destroy the Ramlak. At first, Lion-O was taken in by the captain's talk of adventure and seeking righteous vengeance, but when the time came to face the Ramlak, Lion-O realised that Tunar had ceased caring about his crew's wellbeing and was completely obsessed with killing the Ramlak.
As the Ramlak caused heavy damage to the Fishmen's ship, Captain Tunar ignored the warnings of his crew and blindly continued to attack the Ramlak with his harpoon. Maddened by his struggles, Tunar laughed as the Ramlak yanked the captain clear of his ship and buried him beneath the waves of the Sand Sea.