After the Underground People captured Shin Hayata, they released their ancient weapon, Telesdon. As Telesdon terrorized a city he emerged from underneath, the Underground People began hypnotizing Hayata to learn what they could from Ultraman. However, they underestimated Ultraman's power, as Ultraman transformed by himself and escaped to fight Telesdon. While Telesdon tried his best, he was of little match for the hero from M78 and was easily brought down by the Specium Beam after a brutal beating.
Telesdon would return months later when Pigmon returned mysteriously in a toy store mumbling about something. The Science Patrol had his sayings analyzed and within time they found out that Pigmon, along with Telesdon and Dorako, were revived by a mystical kaiju by the name of Geronimon. Geronimon threatened to revive sixty monsters and conquer Earth. Telesdon awoke with Dorako on an island. The two clashed for a short time, but they were too tired to continue. The Science Patrol traveled to an island to defeat the creatures. After Dorako was killed Telesdon was quickly taken down as well by the Science Patrol's weapons, but they awoke Geronimon and made him angry.