Excalibur

Mumion hört eines Tages die Sage vom Schwert Excalibur. Er beschließt, das mächtigste Schwert aller Zeiten in seinen Besitz zu bringen, um die Thunder Cats endlich zu besiegen.

The Ancient spirits of evil show Mumm-Ra the story of King Arthur, and explain to him that the strongest sword that ever existed was Excalibur, Arthur's weapon. Mumm-Ra disguises himself as Arthur, and returns to lake where the sword is guarded by the lady of the lake. Fooled by his disguise, the lady gives Mumm-Ra Excalibur. The disguised Mumm-Ra challenges Lion-O to a dual, and Lion-O foolishly accepts the challenge. The sword clash, and Excalibur is victorious. The eye of Thundera is split in two, and the Thundercats become powerless. Merlin, Arthur's teacher and a famous magician stops Mumm-Ra from destroying the Thundercats, and restores the eye to its original state.

Mumm-Ra toma la forma del Rey Arturo para poder reclamar a la más poderosa espada de todos los tiempos, Excalibur, para poder destruir de una vez por todas a la Espada del Augurio.