This is the first season after the pilot episodes. This season was released in December 2011.
The season begins with the return of Lord Garmadon by attacking the Jamanakai Village after his disappearance. Ninjago experienced a time of peace during his absence. As such, the Ninja became lazy and complacent. Instead of continuing their training, the Ninja resort to playing video games and eating junk food. Llyod, the son of Lord Garmadon, mostly mischievous, releases the five warring tribes of Serpentine, a race of snake-people who once ruled over Ninjago before being sealed away in underground tombs. They are led by the scheming Pythor P. Chumsworth, last of the fearsome Anacondrai. They are here to seek revenge for being sealed away and they do so by awaking the Great Devourer. To both the Serpentine and Lloyd, the Ninja spin into action to continue their training, make new allies to unlock their True Potential and they discover the identity of the legendary Green Ninja.
As this season has long since past, the Lego sets are mostly discontinued. Instead, Lego released the Lego Ninjago Legacy sets in January 2019 to feature the classic sets from Season 1 and 2. Truth to be told, my kid still asking for the original sets from Season 1 as they relate more closely to the show and some of the minifigurines does not appear in the Legacy set.