Complex sentence: She returns in later episodes near the end of the series run as one of the main villains, and when the team returned to Shuggazoom in "The Ghosts of Shuggazoom", she was revealed to be behind everyone turning into zombie like ghosts.
Split into simpler sentences: She returns in a later episodes near the end of the series run as one of the main villains. Later the team returned to Shuggazoom in "The Ghosts of Shuggazoom", later than she was revealed to be behind everyone turning into zombie like ghosts.