Monolith of Evil Super Friends : Season 3 Episode 12

Solomon Grundy convinces the Legion of Doom to find a "Monolith of Evil" which gave him his powers. But when four of the Legion's members can't retrieve it, The Riddler tricks the Super Friends into fetching it for them. However, Riddler is in for a surprise when the Super Friends learn the truth of the Monolith's powers and use it to put The Riddler and the rest of 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.