Locket of Lies (S03E14)

In Thundera, Mumm-Ra devises the Locket of Lies and has Mu-Mutt conceal it in the Valley of the Snarfs. Eggbert and Oswald Snarf discover the locket and reach out to the Thundercats for assistance. However, their communication is interrupted, prompting Lion-O, Cheetara, Panthro, and Tygra to journey to Thundera to investigate. Once there, the locket guides them to an ancient building, but suddenly, the ground collapses, plunging them into a well. Mumm-Ra appears and warns them against trying to escape, but the Thundercats refuse to give up. As the walls close in, their attempts to break free prove futile until Lion-O harnesses the power of the Eye of Thundera and the Cat Signal, allowing them to break through and escape.