After the battle with the Serpentine, Lord Garmadon escaped with the Golden Weapons. He recruits the remaining masterless Serpentine and merges the Golden Weapons into the powerful Mega Weapon. As the Garmadon becomes ever more stronger, the Ninja starts to train Lloyd, who is revealed as the Green Ninja, so that he can fulfil his mission to save Ninjago and also to face his father one day.
In this season, Lloyd grown into a teenager and he unites with his mother Misako. Garmadon escapes to the Island of Darkness and allies with a disembodied voice called the Overlord. He gains control over the Stone Army and traps the Serpentine underground in the process. Together with Misako, the Ninja travel to the Island of Darkness to stop Garmadon. The Overlord is then revealed to be the dark lord from the prophecy. He possesses Garmadon and heads to Ninjago. After they getting out of the Island, Lloyd uses his newfound Golden Power to defeat the Overlord, purge Garmadon of his evil, and becomes the Golden Ninja.