After years of peace, Ninja masters Kai, Jay, Zane and Cole are forced to come out of retirement to take on Lloyd Garmadon, the son of their archenemy. When Garmadon releases an army of sinister snake people to help him conquer the land of Ninjago, his evil plan goes awry as he loses control. Soon, Garmadon is himself taken prisoner by the manipulative snakes! In an unlikely twist of fate, Garmadon must join forces with the ninja to stop an enemy that prophecy warns will cast their world into eternal darkness.
The ninjas are snapped out of their post-hero complacency when Lord Garmadon's young son Lloyd shows up and tries to pick up where his father left off.
Back in training mode with the looming threat of Lloyd and the Hypnobrai, Zane wanders after a Falcon and lands himself in a heap of trouble.
Lloyd unlocks a second tribe - The Fangpyres - to help him regain control. The Ninja are busy setting up their new HQ that Zane discovered, but are called to duty when the Fangpyres attack the village where Jay's family lives.
After the Fangpyres join forces with the Hypnobrai, Lloyd awakens Pythor - the last remaining snake of the Anacondrai tribe. Pythor steals a map from him that will show him where the remaining two snakes tribes dwell.
Lloyd moves in and tries to make nice by helping out with chores, but he just gets in the way. Pythor has awoken the Vipoids and the Constrictaurs and an all out snake war has taken over Ninjago.
Pythor declares himself to be the destined leader who will reawaken The Great Devourer - an ancient beast who can't be killed and will consume all of Ninjago.
When the four ninja follow the mysterious falcon into the woods, they stumble on a hidden work shop where Zane learns the secret about his past and in the process, he is the first ninja to unlock his true potential.
Jay and Nya have to cut their first date in Mega-Monster Amusement Park short as the Serpentine are on their way to retrieve the first of four fang blades to be used to awaken the Great Devourer.
The four ninja go undercover as a dance troupe and enter a talent contest in their quest to win "The Blade Cup" where one of the fang blades is hidden.
When Garmadon moves in to search for Lloyd, the ninja learn that they must work together to find him. It is believed that the green ninja will be Lloyd.
When the ninja are captured trying to find the Serpentine's inner sanctum,and Lloyd's rescue mission fails; It's up to Garmadon to save them.
As Pythor is preparing to finally unleash The Great Devourer, the ninja are in a race against time to the lost city of Ourobouros.
Disaster threatens as the ninja must fight to defeat the all consuming Great Devourer in a desperate attempt to save Ninjago.