The Ninja finally arrive on the Dark Island, where the Stone Army prepares for the final battle and Garmadon mines Dark Matter, the purest of Evil from the heart of the island, to build a Super-Weapon that can turn the tide of the war. The Overlord also introduced his daughter to Garmadon.
Meanwhile, the Ninja learn that the Temple of Light is where they can both receive their elemental powers and where Lloyd can gain the skill of the Golden Dragon, a fighting style practiced only by the First Spinjitzu Master, after striking the 'Instrument of Peace'.
The Tinkerer and Nya meanwhile builds the Ninja new vehicles: a drill-tank for Cole and a robot for Kai. As the Stone Army searches for them and Sensei Wu, Misako, the Tinkerer and Lloyd guard the hidden Bounty, the Ninja infiltrate Garmadon's camp and Zane finds and retrieves his falcon, with Jay locating the Temple while he is gone.
Zane succeeds, but is spotted and the Ninja have to save him. Cole caught a glimpse of blonde hair hiding behind a tree, before having to run. Running from the army, they narrowly escape and go back to get the machines. The Ninja head for the Temple of Light, narrowly avoiding capture by the Stone Army.
Inside the temple, they find murals depicting all their major victories, surprisingly Cole's cousin Aria was also in one of them. The one that showed them right now. In the mural Aria was standing near the doorway behind all of them. The ninjas looked around, but Aria wasn't there.
"Are we supposed to have Aria with us?" Zane asked
"The mural says she's here, but she's not" Cole said
"if Aria's supposed to be here did we mess up the prophecy somewhere along the way" Lloyd questioned
They find a great bell hanging above a strange design on the floor where the Ninjas' symbols reside. Lloyd looked at his symbol in the middle and saw something else next to his.
"Guys their's a purple symbol next to mine!" Lloyd shouted
"We are missing someone!"Jay said freaking out
"We are missing Aria! She's the Overlord's daughter! Her symbol is the purple one!" Cole shouted
"Aria's the Overlord's daughter!" The ninjas shouted
"But why would she be in the middle?" Lloyd asked
"I don't know" Cole said
All the ninjas are panicking, this won't work unless they have everyone. The stone army was getting closer they didn't know what to do. They heard the doors close and they all looked over to see Aria.
"I'd think closing the doors would be the first thing you do" Aria said breathing heavy, she's tired from something
"Aria" Cole said going over to her
"That's my name, what's up cousin" She said
"We need you to go in the middle and stand next to Lloyd" Cole said
All the other ninjas weren't sure about this, she is the Overlord's daughter after all.
"W-why" she stuttered, sounding a bit scared
"It's alright Aria, please just do it" Jay said
"It won't hurt you at all, please" Kai said
Aria nodded unsure, but went over and stood next to Lloyd. While the ninjas were getting into position, Lloyd held her hand and whispered something to her that calmed her down a bit.
Lloyd strikes the bell, the 'Instrument of Peace', and activates the power of the Temple, gifting the four Ninja with Elemental swords and kimonos.
They then feed their power into the center just as the Stone Army attacks, imbuing him with his full power. Aria felt new power awaken inside of her, her entire body was in pain and she passed out. With the ninjas new powers, they defeated the Stone Army.
Lloyd went and picked up Aria, after he defeated the army.
"Lloyd maybe we should leave her here, she is the Overlord's daughter" Kai said
"But she was with us in the prophocy, it has to mean something" Lloyd argued
"that is true, maybe we should ask Mesako" Zane suggested
"And if not we keep her as a prisoner then?" Cole asked
"I guess" Lloyd said
The Ninja head back to the bounty to get ready to face the final battle. But the Celestial Clock is still counting down, and the Overlord tells Garmadon that when it reaches zero, there will be nothing to prevent Darkness from winning.
The Overlord was in fact the one who told Aria to go to the temple, knowing that she had to go as well. Aria's hardest battle was starting within her. He knew his daughter would choose him over the ninja, the actual ultimate weapon being his own daughter. He will get his daughter back from the ninjas.