The Lost City of Ouroboros

The Lost City of Oraborus (it is unknown if this is the correct spelling) is a buried Serpentine city. At the center of it is an arena with a statue of the Great Devourer.

Background
Pythor and Skales unearthed it, and attempted to get the four Serpentine tribes to unite. All the Serpentine wanted a fight, so Pythor challenged the four snake Generals for their staffs. Pythor beat them all, but then Lloyd Garmadon, who was disguised as a Hypnobrai serpentine, dropped something, revealing himself. Pythor then captures Lloyd, and the Ninjas come to the rescue. Pythor then pits the ninjas against Samurai X, who isn't really attacking. Samurai X lets them escape, defeats a few more Serpentine, then escapes herself. Then, so far, Oraborus is not seen in another episode.