Based in Stiix with his airship R.E.X., he is hired often by Master Chen for important tasks such as capturing Zane and releasing the banished master from the Cursed Realm.
Up until the destruction of the Obsidian Glaive, Ronin was a memory thief known to remove people's memories and replace them with lies about their past.
Ronin, at one point, became indebted to Soul Archer, who threatened to have him banished to the Cursed Realm if he didn't pay him back. Ronin was reluctant to pay him, but after he was banished to the Cursed Realm, the deal had seemingly disintegrated.
After Ninjago: Rebooted
Following the The Overlord's destruction, Ronin captured the newly-rebuilt Zane and P.I.X.A.L. and sold them to Master Chen so he could Zane as bait lure the other four ninja into participating in the Tournament of Elements.
In Shadow of Ronin
Ronin then feared that the Soul archer may return to Ninjago, following Chen's banishment to the Cursed Realm, Ronin planned to free him using the Elemental Forges in return for a large amount of money that he could use to pay his debts With the Soul archer if he returns, Knowing that the Ninja would no doubt interfere with his plans, he sent several of his warriors to the monastery atop Spinjago where they enlisted as Dareth's adult class to get close to the Ninja,
After his men were easily defeated by the Ninja, Ronin himself arrived in stolen samurai armor and lured the Ninja to the top of the mountain, destroying the village as he went. When the Ninja cornered him, Ronin used the Obsidian Glaive to remove their memories, yet was only able to erase a few years before Wu fended him off. The memory thief claimed that he had done what he came for and escaped in R.E.X..
Trying to get the obsidian weapons
To make sure that the Ninja wouldn't regain their memories, Ronin sent his forces to Kryptarium Prison to steal the map to the Inky Lemonberry from Hibiki. They were unable to obtain it before the Ninja arrived however, though by then, Ronin had used the Obsidian Glaive on the Serpentine to make them believe they were still at war with the Ninja. He sent the Constrictai to claim the Obsidian Scythe, but they failed.
Ronin and his forces attacked the Ninja again at the Fire Temple while they were obtaining the Obsidian Sword. Ronin himself arrived at the temple in a large mech just as the Ninja were leaving, but the mech, however, proved to be no match for the power of the Ninja. Ronin was forced to retreat again in R.E.X., but not before he activated a device that would cause the volcano to erupt. The ninja just barely managed to escape in time.
While the Ninja journeyed to the Frozen Wasteland, Ronin constructed a new power source for the Nindroids, and used them to attack Ninjago City as a diversion to buy him time to find the Lightning Forge. He returned to the Floating Ruins just as the Ninja deactivated the power source, and used the forge to attack them, this forcing the Ninja to flee.
stealing all The Elemental forges
Ronin sent his goons after the Forge of Fire while he himself found the Forge of Earth. He then went to the vault of Ice only to find the Ninja there with both the Fire and Ice forges. Ronin ambushed them with the Lightning Forge, though, Dareth and Zane managed to escape. Ronin caught up to them, however and threatened to bury the rest of the Ninja and Wu in dirt unless they hand over the Fire and Ice forges. Dareth countered by attacking Ronin with the two forges, unintentionally creating water, which when Ronin added lighting, shocked and discombobulated the Brown Ninja. Ronin grabbed the remaining Forges and left, his intentions now set on finding the Primal Fulcrum.
Altering Misako and getting the Primal Fulcrum.
Ronin used the Obsidian Glaive to alter Misako's memory to believe that the Ninja had betrayed her. He then sent her to the Fangpyre Tomb to find any clues to the Fulcrum's location. A Samurai that had been secretly watching her reported back to Ronin that the Fulcrum was hidden in Hiroshi's Labyrinth, and Ronin journeyed there to find it.
When he entered the inner chamber where the Fulcrum was kept, Ronin found the Ninja trapped as Misako had tricked them into activating a fail-safe. Misako ran to him, relieved that he was there and expressed that she hoped she did a good job in trapping them. Lloyd however, became furious at what Ronin had done to his mother, and managed to break one of his arms free. He fired a green beam at the Obsidian Glaive, destroying it. With his key weapon no more, and its effect starting to wear off on Misako and the rest of the Serpentine, Ronin mocked the Ninja before he left with the Fulcrum. To ensure he wouldn't be followed, he destroyed the entrance to the room.
Returning to Chen's island
Ronin then traveled to Chen's Island to finish his plans, but the Ninja manage to break free in time and traveled to the Island to stop him. Ronin then gave the orders to his troops to throw everything they had at them.
After the Ninja find Ronin in Chen's Palace, he had already manage to put up a force field around himself and the Fulcrum, as he began to place the Elemental Forges on the Fulcrum. Wu then pleaded him to stop but Ronin refused, placing the final Forge on the Fulcrum and opening a portal to the Cursed Realm.
Final battle and escape
But the Ninja did not stop and instead, entered the now giant sized portal on their Elemental Dragons and the Ultra Dragon to stop him once and for all. After they had searched different portals to find him and manage to build an entrance to the portal he was hiding in, they were finely standing face to face with Ronin for one last time, but Ronin then revealed a triumph card. Using the remaining power of the Elemental Forges, Ronin conjured a giant elemental mech and fought the Ninja. But as the battle continued, the Ninja managed to destroy each of the Forges that powered his elemental mech, until they where all destroyed, and Ronin was then forced to flee on R.E.X. once more, but not before he saw a giant, green, ghostly arm (presumably the Soul archer himself.) coming out of the now closing portal, Ronin then managed to escape.
Ronin later quits being a mercenary and fires all his warriors, he then sold R.E.X. To buy a shop so he can get more money to pay his debts with the Soul Archer.
In Ninjago: Possession
Ronin stole Sensei Yang's Airjitzu scrolls from the ancient library of Domu and returned to Stiix. He was also briefly seen at the Biker Tavern as Morro arrived and left before he summoned Wrayth.
stiix and stones
As Ronin was setting a pot out that hid the scroll at his shop in Stiix, the Ninja arrived seeking it. The thief attempted to sell them weapons such as Aeroblades or Jadeblades, but they were relentless in asking for the scroll and he offered the price of 200, but raised it to 400 when he learned of its value. Kai attempted to barter with him, but due to his poor negotiating skills, they settled on the price of 450. After the Ninja left the shop in search of money, Ronin pulled the scroll out and inspected it.
That night, he was confronted by Soul Archer and Morro who also sought the scrolls. Ronin tried to stall by trying to purchase the Allied Armor of Azure, but they were interrupted when the Ninja arrived. After Morro escaped with the scroll, he rescued Kai and told him there was another way to learn Airjitzu: in exchange for this information, however, he had the Red Ninja give him all the Ninjas' shares of the tea farm as compensation for his shop being destroyed.
The temple on haunted hill
Ronin comes to the tea shop and tells Misako, Nya, and Wu about the deal he and Kai made. When a customer is leaving, Ronin takes the treat Misako gave the man and points out it's a business, not a charity. Nya pays him to take her to her Samurai X Cave. On their way, Nya gets Ronin to reveal that he made a bet with the Soul Archer, and if he did not pay him back, then his soul would go to the Cursed Realm. When they find out that Morro have already arrived in the cave, he uses an Aeroblade to take out one of the Soul Archer's arrows. After Nya's mech got possessed, Ronin saves Nya and takes her outside where the ghosts try to take Ronin's R.E.X. but fail when Nya makes it rain. Ronin then told Nya that she is a Water Ninja.
Ghoultar was brought aboard the Bounty and Ronin questioned the ghost along with Wu and Nya. However, when the ghost refused to answer, Wu decided that the time would be better spent training Nya and the two left, leaving Ronin in charge of the prisoner. Later when Kai got the Sword of Sanctuary from Morro, Sensei Wu says they they can now find the Tomb of the First Spinjitzu Master, though Ronin killed everyone's mood by pointing out they still didn't know where the tomb is.
The Crooked Path
While the ninja set up a ghost security system and Wu and Misako try to figure out the last clue, Ronin washed R.E.X. while observing Nya's training. Upon hearing she unlock her powers after overcoming her fear of failure, Ronin told her not to try so hard: as a result, she reversed the falls of the droplets while lecturing him on why she works hard. Before he could get back to washing R.E.X., he was telepathically contacted by Bansha, who told him to bring Morro the Sword of Sanctuary in exchange for removing his curse.
He began to look around the tea shop for it only to nearly get caught by the ninja. As they discussed how they could find the tomb, Ronin snuck out and went to search in the side buildings only to find Nya with the sword, having picked up on his plan due to his advice. The two began fighting, though it ends with Ronin getting the sword. As he attempts to get away, he is surrounded by the ninja who end up falling for their own ghost traps. He enters the shop and is blocked by Wu and Misako though uses the sword to counter their moves and escape out the back. He then fooled them into thinking he escaped in R.E.X. by setting her on autopilot and sailed down a stream on a raft only to be caught by Nya. Although she learned how to reverse water, she wasn't strong enough to pull Ronin's raft back giving him the chance to escape.
He soon arrived in Stiix and found out the Ghost Warriors were hiding out in his old shop. After Ghoultar confirmed he brought the real sword, Morro allowed him his soul back but changed the deal: he now wanted Ronin to capture the ninja so they wouldn't interfere with The Preeminent's return. Ronin refused as he now saw the ninja as his friends, something the ghosts found hard to believe. However, he wasn't allowed to leave and was possessed by Morro so he could send them off to the Caves of Despair. Afterwards, he left Ronin in Stiix while he, Soul Archer and Bansha took Lloyd to find the tomb and Ghoultar went to finish off the ninja, claiming he was no longer of any use to them. Ronin then sent R.E.X. to save the ninja and explained everything in a recorded message, giving them the coordinates to the real tomb, wishing them luck in stopping Morro and telling them this would be the last they hear from him and if Nya wants an explanation as to why, it would be because he cares.
Curse World Part I
Staying in Ninjago City during New Year's', Ronin ate at Chen's Noodle House and made friends with Skylor. While watching the festivities at Stiix, he learned of the Ghost attacks and traveled there in R.E.X., arriving just as Lloyd began fighting Morro. Using all the money he made, he dumped it on his shop which Morro was levitating in midair, causing it to come crashing to the ground, though couldn't find Morro.
Curse World Part II
Ronin soon began ordering the civilians to get on the ferry and obtains the Sword of Sanctuary to fight off the Preeminent's tentacles. When everyone is boarded, Ronin battles Morro over the Sword, which he eventually lost. He then took to driving the ferry until the Preeminent's destruction at Nya's hands.
Masters of Spinjitzu
Rise of the Serpentine
The Green Ninja
Tournament of Elements
Day of the Departed
Hands of Time