In the city of Stiix, Jay, Zane, Cole, Kai, and Nya gather around the remains of Ronin's pawn shop, as the Preeminent's tentacles emerge. Civilians desperately flee to the docks, where Master Wu, Misako, and Ronin agree that they need to evacuate the city. The Preeminent fully emerges, with the Ninja unsuccessfully attempting to subdue it.

Meanwhile Morro and Aria are dueling throughout the city. Morro using the sword of sanctuary to keep ahead of Aria's upcoming attacks.

"The more souls the Preeminent takes, the bigger she gets. Say goodbye to your loved ones, and say goodbye to Ninjago!" Morro shouts

Aria slams the ground causing the docks to break, Morro quickly jumps onto a building and Aria follows. As the Ninja battle the Preeminent, Lloyd awakens in the Cursed Realm and flees almost immediately when he sees a group of ghosts. 

Lloyd runs through the Cursed Realm, and suddenly, he finds his father bound in chains on either arm.

"Dad!" Lloyd shouts

"Lloyd?" Garmadon looks up and Lloyd hugs him "My son"

"I'll get you out of here, Dad" Lloyd tries to break the chains

"There's no use. These chains will not break" Garmadon tells him

"Where are we?" Lloyd asks

"The Cursed Realm is the Preeminent, and the Preeminent is the Cursed Realm. Son, you're in the belly of the beast" Garmadon replies "But if you're in here..."

"Morro is the Green Ninja and he's stolen the Realm Crystal" Lloyd explains "I tried, Father..."

"You must not give up. If he has the Crystal, all is endangered" Garmadon says 

"Even Lord Aria, you know the Overlord's daughter, is helping us" Lloyd tells him "she has this sword that can cut through ghosts, but I don't think it's enough"

"Aria's hellfire can burn through the ghosts souls and the Preeminent if she unlocks it" Garmadon says "you must return and help, if she unlocks her true potential she will be dangerous for all, but it might be your only hope"

"You want me to help the new Overlord to unlock her true potential!" Lloyd shouts "No way-"

"Son, long ago their was a time when Aria was the pupil of Wu" Garmadon interrupts

"...she was.. a ninja in training" Lloyd says confused

"indeed" Garmadon nods "Son, what is the best way to defeat your enemy?"

"..." Lloyd stares at him "to make them your friend"

-

In Stiix, the Ninja continue their desperate battle against the Preeminent and Morro's army of ghosts. Wu and Misako arrive, telling them that their only hope now is to flee the city with its citizens. The Ninja flee the scene, heading to the docks where Ronin slashes apart the Preeminent's tentacles to allow citizens to get on the ship.

"We need to get this ship to sea to put as much water between us as possible" Wu orders

"No problem" Ronin cuts the rope "Maybe one problem" He sees Morro land in front of him.

"It's Morro!" Cole shouts

"I thought he was fighting Aria!" Kai shouts

"Look out, Ronin!" Jay shouts

Ronin and Morro fight. Morro laughs as he knocks the sword out of Ronin's grasps. Then Lloyd, in Garmadon's robe, jumps in and takes the Sword of Sanctuary from Morro.

"What? You again?" Morro asks surprised

"Yeah, I'm back. I believe you have something of mine" Lloyd says and Morro looks at the crystal and attacks him

"Ronin, get to the ship and protect the people! Ninja where's Lord Aria, we need her hellfire!" Lloyd shouts

"Morro and her were fighting in the tower, we don't know what happened to her after that" Kai replies

"Then sever the stilts, we need to drop the Preeminent into the sea" Lloyd orders "If you see Aria tell her that their's no way she'd be able to defeat us how she is! Just edge her on!"

"What?!" Jay shouts "why do you want us to anger the girl who wants to kill us?!"

"Never mind that, we're on it Lloyd" Cole says

"What about you?" Zane asks

"Just let me handle the blowhard" Lloyd replies

"You think you're better than me? No one is better than me!" Morro shouts and they start fighting.

-

Aria cuts through more ghosts that were around her. Morro's army of ghosts were all targeting her now, that's what gave Morro the ability to escape from her.

"Damn it!" Aria shouts

As Lloyd battles Morro, the Ninja sever many of the stilts, which causes the Preeminent to begin falling towards the sea. Morro orders his army to protect the Preeminent, as he and Lloyd are thrust into a battle that jumps from realm to realm.

Back in Stiix, in order to prevent the Preeminent from being killed, Morro's army of ghosts attach temples and buildings to its body to create a massive "suit" for it that would give the beast legs and prevent it from making contact with the water.

Aria makes her way to the Preeminent slashing apart the ghosts to stop them from helping, it seemed futile though because they just reappeared minutes later.

With help from Morro's army of ghosts, the Preeminent moves slowly through Stiix, heading towards the ship as it flees from the city. Kai, Cole, Jay, Zane, and Nya return to Stiix using Airjitzu, helping Aria battle the ghosts and attempting to deal with the Preeminent.

"...oh yeah" Kai mutters before turning to Aria "hey princess!"

"what?!" Aria asks after slicing another ghost

"Are you having trouble keeping up?" Kai taunts "you seem to be struggling"

Aria glares at him before using her katana to sent black energy blades at ghosts cutting through their souls, destroying them completely.

"...hey guys I think Lloyd was right" Kai turns to them "we gotta edge on Aria, her anger makes her stronger"

"Of course" Cole says "the power of dark feeds off sadness, fear, and anger"

"The fear of the citizens, and her own anger will raise her power" Nya tells them "but Lloyd also said to add she couldn't defeat us with her current power, what would that be about?"

"Perhaps Lloyd is trying to get her to unlock her true potential" Zane suggests

"Is he trying to kill us!" Jay shouts

When the beast makes it to the docks, it is initially stopped by the water, but with help from the ghosts, it manages to wade into the sea. Master Wu orders everyone to throw anything they don't need off the ship so they can move faster.

In the meantime, Morro and Lloyd go from realm to realm, including the Underworld and the Realm of Madness. Back in Stiix, the Ninja continue battling Morro's army of ghosts, defeating such adversaries as Soul Archer only for them to re-emerge from the mouth of the Preeminent. 

"We can't stop it, the best thing we can do for the time being is protect the ship and leave this to Aria" Nya says "she's the only one that can destroy them"

"right" Cole agrees

"i don't know what Lloyd was thinking" Kai says glancing at Aria "but anger isn't going to make her unlock her true potential"

"..what does unlock a Overlord's true potential?" Jay questions

The ninja all regroup with the civilians. Aria keeps fighting the ghost, not every time was permanent, it was rare when she was able to hit their core where their souls were.

On the ship, Ronin tells Wu that they only have enough fuel to get back to Stiix, and not further away from it towards Hallows Trench. Kai then has an idea to drown the Preeminent using the trench, as it wouldn't expect the sheer drop. 

The ship continues on, but just as it passes the trench, the Preeminent knocks off its rudder, stopping it completely as Morro returns to Ninjago, having trapped Lloyd in a separate realm. The civilians on the ship run around in a panic, but Nya stands still.

Encouraged by Wu telling her not to be afraid to fail, Nya unlocks her True Potential. In doing so, she creates a massive tidal wave that crashes into the Preeminent, sending it toppling forwards but it stands back up.

"That's not good" Jay says worriedly

Aria turns to look up where Morro was laughing. Aria glares at him and teleports behind him, he turns his head and moves quickly as Aria slashes down, he nearly dodged it.

"Hah, what are you so angry about?" Morro laughs "missing someone?"

"Where's Lloyd?!" Aria demands

"You're so-"

"I SAID WHERE'S LLOYD" Aria screams

"...heh.. hahaha" Morro laughs "I trapped him in another realm, the green ninja is gone, you should thank me for getting rid of him. You can take over Ninjago with ease now"

Aria's eyes widen and shake "y-you..." her eyes glow purple "you bastard!"

Morro is hit with a dark energy beam and he holds where it hit.

"You're the Overlord you idiot!" Morro shouts "you're supposed to take over Ninjago!"

"I don't want it" Aria says "not if he's not in it!"

"Oh come on!" Morro shouts "you can't tell me you actually love him!"

"I do!" Aria shouts "I love Lloyd! And their's no point in taking over Ninjago, if he's not here with me!"

Aria's eyes turn into slits and a dark beam shoots into the sky. Everyone on the boat screams in fear and the ninja look over.

"Sensei what is that?!" Jay asks

"...a Dark Lord's true potential" Misako replies

"Her dragon form" Wu adds

"Dragon!" the ninja all shout

A roar is heard in the sky and Aria is revealed to have turned into a black dragon. She powers up an energy beam and it shoots out from her mouth at the Preeminent who shrieks in pain.

Aria looks at the boat and roars at Wu.

"Everyone take cover!" Wu orders

Everyone quickly gets down and hides behind things. The Preeminent turns to face Aria just as she roars black fire at it. They heard the Preeminent screech in pain even louder then before as the fire burns it, the water not effecting it at all.

"So that's Aria's hellfire" Cole says amazed

"This is insane!" Kai shouts

"We're so dead" Jay whines "we've gotta fight that one day"

"oh no" is all Zane says

The fire starts burning through the Preeminent and it starts dissolving into the water, destroying the Cursed Realm and killing all its inhabitants, with the Cursed Realm pulling all of the ghosts into the water except for Morro, who stays above the surface.

Everyone cheers now that the Preeminent has been defeated. Wu summons his Dragon and finds Morro struggling to break free of the Preeminent's grasp.

"Take my hand" Wu says extending his hand out to him

"Why? So you can take the Realm Crystal and use it to find your own prized pupil?" Morro questions

"You are all my prized pupils, but none of us can do this alone. You're strong, Morro, but it takes others to make us stronger. Even me. Take my hand, so we can be stronger together. Please, Morro!" Wu begs

Morro grabs Wu's hand "You can only save those who want to be saved. I'm sorry. Goodbye, Sensei" he gives Wu the Crystal before letting go and is then pulled into the sea, where he dies as he is permanently dissolved by the water

Wu and the others return to Stiix where Aria is standing at the docks. The ninja walk over to her.

"I hate to admit it.. but you saved the day" Kai sighs "thanks"

"I was just doing my job" Aria crosses her arms

"I believe.." Wu walks over and hands her the realm crystal "this belongs to you"

Aria tosses it into the sky as it glows, a portal opens and out came Lloyd. Aria catches the crystal and it stops glowing.

"Lloyd, you made it" Misako says happily

"And so did all of you" Lloyd looks at them

Zane smiles "Good to have you back. You just missed—"

"Oh, I know what I missed. I caught a glimpse of what would happen next" Lloyd grabs the Sword of Sanctuary "and knew Morro had to return alone. Just 'cause I'm the Green Ninja, doesn't mean I have to save the day. Especially when I have friends to rely on"

Misako smiled "And that's why destiny chose you"

"It appears your father's robe has imparted wisdom, but you still have a lot to master to earn the Sensei title" Wu says

"If that's the path I'm on, I'll take it one step at a time. The Cursed Realm is gone...and so is my father...but I know we're all in a better place" Lloyd says

Aria tosses the realm crystal up and down impatiently.

"Lord Aria" Lloyd approaches her "..thank you"

"Of course" Aria stops tossing the crystal "but I was only-"

"Right" Lloyd smiles "doing your job... so, see you next time you try to kill us?"

Aria stares at him confused "...yeah"