5 fearsome episodes:
"Island of the Body Snatchers"
The trio investigate a sector called the Mystery Zone where several ships get wrecked on an island. They learn the evil witch Circe is responsible as she needs a young sorceress to overcome a curse in which she will turn to stone if she leaves the island. When Ariel arrives with Thundarr and Ookla, Circe gets her opportunity as she switches bodies with her and becomes a threat to the others as she tries to leave the island.
"Last Train to Doomsday"
Thundarr, Ookla, and Ariel are in pursuit of a mummy-like Janus after he and a race of hawk mutants attack villages and the train route of Tye (the former swamp urchin from "Harvest of Doom"). The group is in for a surprise when it turns out Janus is actually Gemini (the two-faced wizard from "Secret of the Black Pearl") in disguise seeking revenge on Thundarr. Tye, from "Harvest of Doom", returns as a train driving "businesswoman".
"Prophecy of Peril"
Thundarr, Princess Ariel, and Ookla battle the evil wizard Vashtarr when he steals the Crystal of Prophecy that can give the details of his downfall. When it shatters in his efforts to retrieve it, the prophecy is foretold as they learn three women will unite to defeat him. One is Maya, an element-shifter buried in the ruins of the old city of Endorr. Another is Cinda, a hermitic barbarian living in the Canyon of Death whose staff grants her great strength. The last is Valerie Storm, a fashion model from Old Earth who is abducted and taken prisoner by Vashtarr himself.
"Fortress of Fear"
When coming to the aid of an escaped slave, Thundarr, Princess Ariel, and Ookla are captured by robots working for the multi-eyed wizard Lord Argoth who wants Ariel as his bride.
"Master of the Stolen Sunsword"
During a battle with Yando (a supposed wizard with unusual magic), Thundarr is struck by red negative lightning which significantly diminishes the power of his Sunsword. The weapon can be restored at the nearby Pool of Power, but it is stolen by Yando who seeks to have the Sunsword's power for himself.