Lloyd Garmadon is taken prisoner by the Serpentine after attempting to spy on them. Other Possible Matches
The Ninja discover that Nya is the mysterious Samurai X. [S1E8] The Snake King
Pythor challenges the other Serpentine Generals in the Slither Pit, winning their staffs and uniting the tribes under his command. 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