The Nightmare Legion first appeared in Season 6 (Iteration 1). It was first mentioned in “The Nightmare Legion Rises”, where Absol and Beanluv (now under the name Executor) were seen in one of its factories. The factory itself was decorated with images of the Miracle Crown, implying there was to be a connection between the two. When Cloud was warped to Imagina, he was informed of the impending threat of the Nightmare Legion. In “The Knux Conspiracy”, it was shown that Knux became a commander of the Nightmare Legion. He then kidnapped Cloud and Switch to take them to Cloud’s Observatory. Knux revealed his betrayal to the Legion and informed the two that the Observatory was being used as its base.
The Nightmare Legion was intended to return in Season 6 (Iteration 2). However, the series was cancelled after nine episodes, and thus did not appear. Its role is unknown.