Harumi narrates her backstory to Lloyd through a series of crystals. She was revived by the Crystal King in exchange for her service which included forming an army of vengestone warriors. She reveals the identity of the Crystal King and that they plan to steal the weapons of Spinjitzu.
Long before time had a name, Ninjago was created by the First Spinjitzu Master by using the Four Elemental Weapons of Spinjitzu; weapons so powerful, no one can handle all of their power at once. When he passed away, his two sons swore to protect them, but the oldest, Lord Garmadon, was consumed by darkness and wanted to possess them all. A battle between brothers broke out and Lord Garmadon was struck down and banished to the Underworld. Peace returned to Ninjago as the younger brother, Sensei Wu, hid the elemental weapons in the far corners of Ninjago.