In Season 6 (Iteration 1), Cloud was warped to Imagina to defeat four nightmares. Each nightmare awarded him with a piece of the Celestial Scepter. In “Morning Realization”, Cloud was able to exit Imagina and retrieve the Scepter in the real world. He then teamed up with Switch, who had obtained the Celestial Stars (an equivalent weapon in a different form), to defeat the Nightmare Legion.
The Celestial Scepter was intended to return in Season 6 (Iteration 2). However, the saga was cancelled after nine episodes, and so it did not appear.