Lloyd Garmadon is taken prisoner by the Serpentine after attempting to spy on them. Other Possible Matches
The Ninja hold a tournament to see whose weapon will glow, believing it will reveal who is destined to be the Green Ninja. [S1E8] The Snake King
The Ninja discover that Nya is the mysterious Samurai X. Lloyd Garmadon is taken prisoner by the Serpentine
If you are looking for a different series, "The Snake King" (or a very similar title) appears in these contexts: [S1E8] The Snake King