Re-reading the first book of the Purple Ninja makes me think about what Katarina's life was before she met the Ninja and reunited with Wu and Garmadon. She went from having little to no friends to having a lot of friends, she became truly happy, and if she hadn't stayed with the Ninja, she wouldn't have been able to heal and grow like how she is right now.

Might be a great AU I could do as a oneshot one day. It would be fun. 

During the daytime, citizens of Ninjago City were enjoying their modern life; People played games on their phones as they walked down the streets, Nelson and Antonia were delivering the daily newspaper to houses, apartments and buildings, and Dareth was trying to impress Gayle Gossip, who seemed...flattered by his efforts to please her.

Everything was perfect.

But the nighttime was when the bad guys came out to play.

Late one night, a noodle truck for Chen's Number 1 Noodle House stops outside an empty warehouse. The back of the truck opens, revealing the Mechanic - who had escaped prison again - and a gang of low-leveled street thugs that were working for him.

They eagerly run towards the warehouse. The Mechanic uses his mechanical arm to bust the door wide open, letting it fall to the ground. "We're in, boys!"

The thugs get a good look inside the warehouse. It was all just old computers and tech junk, nothing valuable. They were very displeased.

"Huh, look at all this old junk." One of them scoffs. The Mechanic grabs him by the collar of his black hoodie and glares at him threateningly.

"Just because it's old doesn't make it junk, just forgotten." He shoves the thug away from his sight. "Find the motherboard!"

The thugs nod and spread out in the vast warehouse, looking for what they came for. He walks down the aisle, as the gang looks around nooks and crannies, in crates and open boxes for the motherboard.

Until finally, he spotted it, on the highest shelf in the center of the warehouse. "There! The top shelf." A thug nods at the request and grabs a ladder. He climbs up on the ladder and grabs the box of the motherboards. But doing so made him fall back down into a crate of styrofoam, while the motherboards spill all over the area.

The Mechanic walks over the thug and grabs him by the collar of his black hoodie. "Careful with those!" He throws the thug out of the crate and quickly but carefully scans his eyes for a specific motherboard.

"What are we looking for, boss?"

There, amongst the scattered motherboards, was a motherboard that stood out like a sore thumb. He grabs it, and examines it happily. It was a dark red and black color, with a strange symbol right in its center. He laughs. The group of thugs gather around him. 

"This is it. A needle in a haystack. A very, very valuable needle."

Suddenly, the lights turn on in the warehouse, one by one, shining down on the Mechanic and the group of thugs.

"Sorry to crash the party, boys!" Nya says. The Ninja, who were standing on top of the aisles. They had heard and saw everything in the cover of darkness. Nya, Cole, Jay, Zane, Lloyd, Kai and Katarina jump down and land mere feet away from the thugs, one by one.

"Guess our invitations got lost in the mail, huh?" Jay reaches behind his back and grasps his hand around his kusarigama.

"But hey, there's always such a thing as being," Katarina summons her daggers with her magic in a to and fro flourish, until she points one of them at the Mechanic. "Fashionably late."

Lloyd puts his hands on Katarina's and Jay's chests. "No weapons, guys. These are just low level thugs."

"My fists are my weapons." Cole punches his fists in the air, eager to fight the Mechanic and his gang.

"I would not classify the Mechanic as low-level. He's suspected in thirty-six unsolved criminal cases." Zane explains to his friends.

"Thirty-seven!" The Mechanic extends his mechanical arm out towards Zane, sending him crashing into several boxes full of tech junk.

Jay gets into his fighting stance. "You're not getting away that easy!"

The Mechanic laughs. "Who's trying to get away?! There are more of us than you!" He looked to his henchmen, who were slowly getting away. They didn't want to risk being captured and beaten by the Ninja.

The Mechanic growls at the henchmen and silently gestures them towards the Ninja. Seeing they had no other choice, the thugs pull out their wooden bats.

"And we're not afraid to use our weapons."

"Says the guys who hired a bunch of wimps." Katarina chuckles, putting a hand on her hip. Jay snickers at the comment.

The Mechanic growls. Using his mechanical arm, he ignites the flamethrower, shooting a torrent of fire at the Ninja, who dodge and move away from the fire.

Jay grabs three floppy disks out of a crate. "I have no problems using these!" He throws him at the Mechanic and the thugs. "Take that, obsolete file formats!"

The Mechanic dodges the files. However, in doing so, the motherboard was knocked out of his hand. Kai, without thinking twice, dives for the motherboard. He lands on the floor and catches it. He breathes a sigh of relief.

But the thugs were going to let him get away with the motherboard. They tackle Kai in a dogpile, trying to pin him down as they try to get the motherboard out of his grasp. He throws it, hoping one of the Ninja would catch it, but instead, one of the thugs did.

The thug with the motherboard climbs up a ladder to get to the highest shelf. Lloyd shoves another thug away and says, "I got him!" He climbs up the shelf the thug was on, and chases him, until they were two aisles down.

The thug gets out his bat and swings it at Lloyd, who jumps back and deflects the junk that was being kicked at him. Cole pins a thug against a wall. "Use the VCRs!"

Lloyd stops deflecting and says in a confused tone, "What's a VCR?" He looks at the thug that was attacking him for answers, but his attacker just shrugs, just as confused as Lloyd.

"It's that old machine Wu watches his ninja movies on." 

Lloyd looks behind him and sees three VCR machines stacked on top of each other. He presses the buttons. "Eject! Eject! Eject!"

The thug, confused by what Lloyd was doing, walks towards him while swinging his back in the air. Lloyd looks at the machines and groans. "Any time now."

After a few seconds, the machines eject VHS tapes at the thug, knocking the bat out of his hands. Lloyd runs at the thug and tackles him head-on, causing them to go over to the next shelf. The motherboard was knocked out of the thug's hands, and the shelf was tipping over fast.

Nya slides on the ground and grabs the motherboard. "Got it!" She says and runs out of the aisle so she wouldn't be squished by the falling shelf. Lloyd jumps off and the Ninja get out of the way, as the shelf finally falls down and traps the rest of the thugs.

However, the Mechanic manages to sneak behind Nya and grab the motherboard out of her hand. She gasps and frowns as the Mechanic escapes.

"I'll take that!"

"Hey!"

"Thanks!" The Mechanic runs out of the warehouse and speeds off in the noodle truck before the Ninja could catch up to him. The Ninja went into the alley, where their vehicles were. Cole rides in his Rock Cycle, Katarina rides in her motorbike, and the rest of the Ninja ride in Kai's ATV. 

The Mechanic looks in his sideview mirror to see the Ninja were following him with vehicles of their own. He activates the claw arm from his truck and has the truck grab a light post to steer the truck around. 

The Ninja get out of the way as the truck drives in the opposite direction. They make a U-turn and continue their pursuit. The truck drives into a few traschans, forcing the Ninja to slow down and avoid the oncoming obstacles.

Seeing what the Mechanic was trying to do, they drive a little faster to catch up to hinm. 

The ATV and the truck were side by side now. "Look out!" The truck rams into the ATV. 

"HEY! Watch the paint job!" The ATV spins away from the Mechanic, leaving Cole and Katarina to pursue the Mechanic by themselves. 

Cole launches a grappling hook at the back of the truck, making sure to get a good grip on it. Katarina summons a magic chain and hook, and throws it at the back of the truck, letting it catch on and grip onto it. 

Cole speeds up and circles around a light post multiple times with his chain. Katarina stops her motorbike instantly and pulls hard at her chain. 

"Oh, c'mon!" The Mechanic groans. The truck jolts to a sudden stop. "So close!" He hops out of the vehicle, planning to make a run for it, but the ATV speeds up. The rest of the team jump down and surround the Mechanic. 

The Ninja get into their fighting stances, just in case the Mechanic was planning to make it extra difficult for them. "It's over, Mechanic! Give it up!" Lloyd says. 

The Mechanic puts his hands up. "I'll be taking this!" Jay snatches the motherboard out of his hand and takes a quick glance at it. He was instantly confused yet intrigued by the strange design of the motherboard. 

The police arrived on the scene minutes later to arrest the Mechanic. A police officer shoves him into the police car and drives away to the police station. 

"Great work, ninja! You guys saved the day!" The Commissioner thanks the Ninja, who watch the police car drive away with the Mechanic inside. 

"Yeah. But what exactly did we save the day from?" Kai asks while he crosses his arms. 

The Commissioner scratches the back of his neck. "Uhh, I don't know yet. The Mechanic's not saying anything, but we'll take him downtown and maybe we'll get some answers then."

Jay pulls out the motherboard from his back pocket and takes another look at it. "Let's go, boys! Pack it in!" As the police officers rush off to their cars, Jay tries to get their attention by showing them the motherboard, but it was useless when the cars drive back to the station. 

"If we only knew what this was for."

"Well, it's a motherboard to a computer." Cole answers. 

"But which computer? There are 3,412,870 computers in Ninjago City," Zane smiles, even to himself. "Approximately."

"But only one secret lair!" Nya points to an abandoned arcade that they were front of. "That's where he was running when we caught him! Maybe that's his hideout!"

The Ninja nod and walk towards the arcade. "An abandoned arcade?" They walk inside the messy, abandoned store and take a look around. 

Nya looks up and sees at least a dozen robo-arms hanging from the ceiling. "Look at all these robo-arms. This guy has an obsession." She says with an eyeroll. 

A robo arms rolls from a shelf and falls on Lloyd's shoulder, causing him to yelp in surprise and throw the object away from him. "Oh, okay, let's make it quick. This place is super creepy."

"No way!" Jay's sudden outburts catches everyone's attention, turning their heads to see him standing in front of an arcade cabinet. He had the brightest, happiest smile plastered on his face. "Do you know what this is?!"

His friends blink at him, clearly having no clue what got Jay so excited. "It's Prime Empire!" He answers for him.

Now it was Cole's turn to smile, however it wasn't as bright as Jay's, and he made a playful scoff. "What?! No way!"

Jay was clapping his hands together with joy and looked like he was going to explode from sheer happiness. "Look at it! It says Prime Empire right on the side!" He gasps. "It's real!"

Katarina clears her throat, stopping Jay's excitement momentarily. "Hey, can you two pretend we aren't all video game nerds, and just explain to the rest of us what this Prime Empire is?"

Jay was more than happy to explain. "Oh, it's this legendary game created by the most famous game designer ever, Milton Dyer . But for some reason, it was never finished and they abandoned it."

He goes to the back of the arcade cabinet and plugs it into an outlet. He stands in front of the cabinet again, eager for it to turn on. 

But nothing happens. 

Bummer. 

"Well, that was exciting." Cole says, the excitement drained from him completely now. 

"Can't have been that good if they never released it." Kai shrugs. 

Zane puts a hand on his hip and pretends to examine his gloved hand. "I find old games to be unchallenging." He says with a raised eyebrow. 

Lloyd nods. "Yeah, I like new ones, where they really make you feel like you're there."

Katarina shrugs. "Eh, I don't like video games. Not my thing. That's why I don't play them." Kai, Cole, Jay, Lloyd and Zane give her a bewildered look. "What?"

"Can we get back on track?" Nya says, clearly annoyed that they were wasting time talking about video games. "There's a lot of nooks and crannies here and we're not even sure what we're looking for, so let's spread out!"

The Ninja nod. "Uh, yeah! Okay, good idea, except I think I should stay here and keep checking in this, uh, area." He gestures with his arms with the room that they were in. Nya raises an eyebrow. 

"Why do I feel like you're just going to fuss around with that broken game?" She says with a suspicious tone. She crosses her arms at the unconvincing statement. 

"Pfft, what?! No, no, I'm just gonna start here first. You know we don't want to miss any clues. Right?" The Ninja nod and began to walk away from the area Jay was in. Nya was the last one to leave, giving her Yin a narrowing glance as she walks away. 

As soon as they were out of the room, he immediately sets to work on the cabinet. 

"He's gonna fuss around with that cabinet." Nya mutters to Katarina. Katarina chuckles fondly. 

"Let him. Besides, I don't think I've seen Jay be that happy over a game," She chuckles again. "He reminds me of his mom sometimes."

"He does?" Nya asks. 

Katarina nods. "His mother Elle, the former Master of Lightning, had a bubbly personality, really talkative, made jokes, and got married to this guy Cliff Gordon. She was part of the first Elemental Alliance, too."

"Really?" Nya marvels. It was rare for Katarina to talk about her past, especially about the Alliance, and when the others ask her about it, she's intentionally vague about parts of her life and would only talk about her time with Wu and Garmadon. 

The first time they asked about it was when the Time Twins and their Vermillion army attacked the city, and she voluntarily talked about her immortality and her siblings. She never spoke of her times with them again, until Cole asked her once what it was like. All she did was shrug and said it was fine, and left it at that.

The others made it a rule to never ask her about that part of her life. 

"Yeah. Of course, the Alliance disbanded to continue on with their lives. They wanted to have families, and you know, enjoy the peace that we fought hard for. It was a good thing while it lasted."

"Huh," The Ninja were walking down a hallway now. "What did you do when they disbanded?"

Katarina was about to lie about that, when Cole commented, "Wow. He's got a lot of hats."

Kai rolls his eyes. " Yeah, who would have thought a guy super into stealing things would have too much stuff?" Cole groans softly at Kai's sarcastic remark and continues walking. 

Jay began uselessly pressing buttons on the cabinet, trying to get it to turn on so he could play the game. "Aww, come on! Just turn on! This is too cool to not get to play one time." He goes behind the cabinet and sees an empty slot. 

"Huh. You need a....a motherboard!" He pulls out the motherboard they stole back from the Mechanic and slides it into the slot. 

The blank screen on the cabinet is now blood red. 

Then, a pulse emits from the cabinet, and goes throughout the entire city. Jay gets sent back from the blast. He screams. 

Zane gets up, intrigued about the sudden, strange pulse. "Uh. What was that?"

Nya and the others look around, also confused about the pulse. "We better keep looking," She spots a door on the other side of the hallway. "Hey! There's a door back there."

The police officers were escorting the Mechanic into the police station. They feel the pulse that came from the abandoned arcade and look around to see what caused it. 

The Mechanic couldn't help but smirk and chuckle. 

It was done. Now all that was left was to press the start button to the game. 

Kids playing in arcades across Ninjago city were playing games on the active cabinets. When the pulse hits, the power goes off in the buildings for a brief moment before turning back on and revealing the same symbol on the back of the motherboard. 

Intrigued by the sudden change to the cabinets on their favourite games, they hit the start button and began to play the strange new game on the cabinets. 

What was stranger was that the new game they were now playing was called Prime Empire. 

Jay gets up, trying to recover from the initial shock from the pulse. 

"Would you like to enter Prime Empire?" An automated voice from the Prime Empire arcade cabinet asks Jay. Jay turns around and gasps. In bright, orange letters were the words Prime Empire in front of the strange symbol from the motherboard. 

He smiles. "Oh ho, don't mind it I do."

He presses the start button and begins to play the game. 

Nya opens the door to the room, and the others follow close behind. It was a mess in there, that was for sure. There were papers skewed all over the floor, post-it notes on the walls and files, and file folders overflowing with more and more papers. 

There was also that symbol hastily drawn all over the room. 

"What a mess! Maybe he should steal a filing cabinet next." Nya remarks. 

On a corkboard behind a computer, typewriter and a stack of files were a few papers pinned to it. "That's the same weird symbol that's on the back of that motherboard."

Lloyd picks up a file folder and nods. "It's everywhere! But what does it mean?"

Suddenly, something turns on, catching the Ninjas' attention. Zane pushes the files aside and was met with an old model of a computer. 

"Did you locate the motherboard?" The computer asks Zane. He turns around to face his friends, wondering what to do or how he should respond. 

"Did you locate the motherboard?!" The computer asks, this time in a louder and more firmer tone of voice. Zane puts his fingers on the keyboard and begins to type. 

Yes, we did.

If whoever was talking on the computer was smirking, they couldn't tell. "Unagami is pleased. Activate the game."

Then the screen blacks out. 

"Who the hell is Unagami?" Katarina wonders aloud. 

Meanwhile, Jay was having the time of his life with playing Prime Empire. "Oh ho! You're going down, ogre! You're the only thing between me and beating this level and I am not letting you fire catapult me again!" 

His feet slide back a bit as he rapidly presses the buttons on the cabinet, but he stands back up and smiles with a a hearty laugh. "Oh ho! Yes! Take that!" He does a victory dance. "Uh huh! What else you got for me, game?

The screen shows the same symbol, flashing the words Level 13. "Congratulations. You have reached Level 13. Would you like to enter Prime Empire?"

Jay's smile widens. "Pfft. Hell yes, I would like to continue!" He presses a button on the arcade cabinet. 

"Now entering Level 13."

The arcade cabinet slowly splits in half. He backs up as the mysterious door slides open, revealing a bright white light. He shields his eyes from the light for a brief moment before taking his arm down and smiling. 

He makes the decision to walk into the arcade cabinet, not giving it a second thought. The arcade cabinet closes behind him. The screen flashes the words Prime Empire again, waiting for the next player to play the game. 

The Ninja walk back into the room Jay was in just seconds ago. 

"Jay! We found a clue!" Nya exclaims. 

"The Mechanic's working for someone who calls himself Una-" Cole stops talking, and all of their faces fall. 

Jay wasn't in the room anymore. 

"Jay?" Lloyd asks, looking around for their friend. 

Meanwhile, hundreds of arcade cabinets in all of the arcades all over Ninjago City were asking players one question. 

Would you like to enter Prime Empire?