[s11e27] Corruption -

A summary of the episode ("The Castle of the Overlord")? More information on Nya's development? LEGO Ninjago - Aired Order - All Seasons - TheTVDB.com

The Ninja pursue Garmadon to the coast. Kai, Jay, Zane, and Cole are forced to stay behind to deal with the newly evil Nya. [S11E27] Corruption

The Stone Army and the Garmatron represent a massive, unstoppable threat compared to previous foes. A summary of the episode ("The Castle of the Overlord")

Based on the title "[S11E27] Corruption," this episode is part of (specifically from the Legacy of the Green Ninja/Season 2 arc often re-indexed, or associated with the Dark Island narrative). and gaining Garmadon's dark abilities.

Before leaving, the Garmatron is tested on Nya. This results in her being corrupted, turning evil, and gaining Garmadon's dark abilities.