The Thundercats are from the planet Thundera and managed to escape from the planet just before it was destroyed. They were pursued by a group of mutants and the ancient devil priest of First Earth, Mumm-Ra. The mutants mission was to steal the 'Sword of Omens' from the Thundercats. During their journey they came under attack from the mutants and only one of their space ships survived, which crash landed on Third Earth. The Thundercats settled in a castle called the Cat's Lair where they created various weapons and vehicles such as the Thundertank.
