In the season finale, Mumm-Ra's forces find the ThunderCats and the Tech Stone in Avista City. An incredible battle ensues for the stone as Lion-O finds himself betrayed by a trusted ally.

Cast: Will Friedle, Emmanuelle Chriqui, Madeleine Hall, Satomi Kôrogi, Matthew Mercer, Eamon Pirruccello, Kevin Michael Richardson, Pamela Adlon, Dee Bradley Baker, Robin Atkin Downes, Michael McKean