On Third Earth, the kingdom of Thundera is being threatened by the evil sorcerer Mumm-Ra, and Lion-O, the young heir to the throne, embarks on a great quest to take his rightful place as king. The unlikely champion must work with his faithful comrades Tygra, Cheetara, Panthro, WilyKit, WilyKat and his loyal pet, Snarf, who join him on his journey to save their world from darkness.

On Third Earth, the kingdom of Thundera is being threatened by the evil sorcerer Mumm-Ra, and Lion-O, the young heir to the throne, embarks on a great quest to take his rightful place as king.