Complex sentence: When he encounters Jestro again, the Cloud of Monstrox uses his evil lightning to control Jestro again as he uses his evil lightning to animate a fortress at Ghoulia to reanimate the Stone Monster Army.
Split into simpler sentences: When he encounters Jestro again, the Cloud of Monstrox uses his evil lightning to control Jestro again where they head to a fortress at Ghoulia. Once there, the Cloud of Monstrox uses his evil lightning to reanimate the Stone Monster Army.