Monolith of Evil - S3.E12

Solomon Grundy convinces the Legion of Doom to find the "Monolith of Evil" which gave him his powers where it revived him from his death. But when he, Grodd, the Cheetah and the Riddler cannot retrieve it, the Riddler tricks the Super Friends into fetching it for them by using a mirage to make it look like the Legion of Doom shrunk the United Nations building. However, they are in for a surprise when the Super Friends learn the truth of the Monolith's powers. They use it to put the Legion of Doom in their place — as the Monolith itself is not inherently evil, but acts upon the thoughts (evil or good) of whoever controls it.