Garmadon was going to join his brother and Nya in rebuilding Destiny's Bounty. He went to ask his son for help but the latter told him that he was going on a fishing trip with his friends as Garmadon was happy they reconnected. Lloyd then asks his father if there were others with elemental powers like him and the Ninja. Garmadon questions Lloyd why he asked him that, to Lloyd's response with nothing. He feels suspicious of his son and then heads towards his son's room where he found at that he casted the fishing rod against the wall and left it there. As Garmadon looks around and questions what is going on, he notices and spots a takeout carton and realizes Chen was involved with son's mysterious behavior.
With this knowledge, Garmadon deduces Lloyd and the other Ninja were going to Chen's Island. He immediately followed them to the docks, where the Elemental Masters began boarding Chen's Ferry. While there Garmadon encountered his old rival Clouse, who is still working with Chen. Garmadon tries to stop the Ninja but they are insisted on going due to the fact that Zane may still be alive and this was a chance to find him. After failing to dissuade his son from going, Garmadon decides to join him on the journey. Clouse initially refuses to let Garmadon on the ship stating there was no room, but Garmadon boards anyway after knocking off a grunt and Clouse allows this act.
On the ferry, Garmadon tells the Ninja about Clouse being a dangerous wizard and Chen's second-in-command. Soon, the Ninja meet various people using different kinds of powers as Kai asks Garmadon why he or Wu never told them there were other with abilities like them as Garmadon explains there were things they didn't want them to know as he tells the Ninja about the Elemental Masters who are descended from previous elemental users. When Kai noted the same went for him and his sister, Garmadon tells a confused Kai that Nya might have the element of Water but it just needed to be unlocked. Garmadon makes note of a few of major Elemental Masters. Clouse then announces to everyone that they're about to reach Chen's Island before calling Chen himself and telling him that Garmadon has returned. Garmadon tells the Ninja that he swore never to return to the island while the Ninja contemplate whether they'll be able to find Zane.
After arriving on the island, Clouse speaks to Garmadon and states that Chen will be pleased to see him again while tensely referring to him as Sensei.
Garmadon reveals to the Ninja that Master Chen was previously his master, during a period in Garmadon's life when he took the path of evil. During the Serpentine War, Chen betrayed the Elemental Masters by siding with the Serpentine before being exiled to his island fortress as part of a deal for his surrender. After the tournament bracket is revealed he is kicked out of Chen's fortress by Clouse, but sneaks back in during the first round. After catching Clouse using his dark magic to sabotage Lloyd, Garmadon attacks him, the grapple enabling Lloyd to claim one of the Jadeblades. He then takes part in the group's discussion regarding the urgency of finding Zane.
After suffering continued ill treatment from Chen's minions, Garmadon joined the others in observing various battles, including Kai's fight with Ash and the confrontation between Bolobo and,Neuro. Garmadon expressed confidence in Neuro's ability to succeed, and was proved right despite Bolobo's early advantage. Unfortunately, the Ninja were soon forced to contend with an unpleasant development: Chen changing the tournament roster so that Jay and Cole were forced to battle each other. He wisely reasoned that the pair would have to reconcile or fail, and was pleased when they renewed their friendship. Unfortunately, Cole was forced to forfeit in order to insure that at least one of them would continue to advance in the tournament.
Garmadon joined his pupils in observing a battle between Skylor and Jacob Pevsner, and noted that Jacob's power over Sound had grown since he had last encountered him. After hearing the Ninja speculate as to whether Skylor and Kai might be related due to her use of Fire, Garmadon revealed that she was the Master of Amber. He would then tell the Ninja that they should try to befriend their competition or they would try to defeat them.
Garmadon and the remaining Ninja were heartened by the fact that they had managed to form an alliance with the other competitors, only for Chen to mislead the group by telling them that his intent was to award his Staff of Elements to the winner of the tournament.
Things start looking up as they learn from a disguised Nya—who had infiltrated Chen's Kabuki—that there was a spy in their midst. The Ninja soon receive a fortune cookie from Skylor that says Cole and Zane will be breaking out very soon as they express relief that Cole manage to find their friends. Garmadon later joined the Ninja in attempting to uncover the spy, providing the helpful hint that a minion of Chen would have an Anacondrai tattoo on their back like his.
Garmadon and the remaining contestants boarded Chen's Blimp and were flown high above the island, where they learned that the next task would be hunting the fugitive Nya. However, as they were dropped onto the island, it was determined that the parachutes left for them by Chen were one short given Garmadon's presence. As he and Lloyd fell, Lloyd struggled to summon his Elemental Dragon, which Garmadon revealed was due to his fear. Both grabbed onto a parachute, and Garmadon attempted to sacrifice himself so that Lloyd could use it, but Lloyd refused. After Lloyd opened the parachute for him, Garmadon who was shocked said "What have you done!?"
A few seconds later Garmadon was happy that his son succesfully managed to summon his dragon. Working together, the pair soon discovered that Nya had left a false trail for her pursuers and a real one for her friends.
Along the way, Garmadon revealed to Lloyd the full details of his previous allegiance to Chen and how he received the title of Lord from him after defeating Clouse. Likewise, he explained their involvement in the Serpentine Wars, including his adding his own signature to Wu's letter to Misako. He also revealed that he had never told Misako or Wu the truth, but that he didn't regret it being that Lloyd wouldn't exist as a result. Lloyd then encouraged him to come clean with his wife and brother, and Garmadon agreed to do so. Unfortunately, they found Nya just in time to learn Chen's true plan: to use the stolen powers to turn him and his Anacondrai Cultists into Anacondrai.
Garmadon, Nya, and Lloyd soon assault Chen's Fortress in a bid to rescue the others and stop Chen's plan. Garmadon was forced to battle Clouse, who gained the upper hand due to his use of an Anacondrai Blade. Captured and imprisoned alongside Nya, Garmadon was mocked by Chen and Clouse, who visited them to taunt them over his victory over Lloyd. Garmadon angrily questioned the location of his son as Chen stated he will take Lloyd's power at the ceremony which Garmadon can't attend as Chen was still hurt at his leave. Nya wondered how Chen beat Lloyd which Chen stated he had help revealing Kai was the one who did so.
Garmadon was angered Chen turned the Ninja against each other as he did their ancestors before grabbing Skylor, attempting to use her as way to be released but Chen and Clouse called his bluff. With Nya, Garmadon was left at the mercy of Clouse's Anacondrai Serpent, while the villains leave though not before Kai winks at them revealing it was all a ruse relieving them. Sometime later, Clouse's pet serpent arrived which Garmadon viewed as karma accrued by his role in destroying the Great Devourer. However, a jailbreak of the Elemental Masters—aided by Cole, Zane, and Jay Roto Jet—resulted in their escape, and they soon intervened in Chen's ceremony returning the powers to the Elemental Masters, forcing Chen, Clouse, and a few henchmen to flee.
Following much of the Anacondrai Cultists' capture, Garmadon was with the five Ninja, exclaiming his pride within the five, saying that they did what the original Elemental Masters could not: stick together. After getting a message from Griffin Turner from Neuro, Garmadon and Cole used the Roto-Jet to help assist in finding Chen's remaining forces and the captive Skylor. Unfortunately, the pair got into a dogfight with Clouse and Chen, the former leaping onto the Roto-Jet to sabotage it. Garmadon exited the craft to engage his former classmate, and knocked him off the plane. Their battle resumed on the ground, with Clouse opening a portal to the Cursed Realm in an effort to rid himself of Garmadon and claim his old title of Lord. However, Garmadon managed to drag Clouse into the portal before climbing over him to escape it, which caused him to remark on his dislike of Magic.
Sadly, Garmadon's victory would be short-lived, as Chen used Skylor's powers to fuel his spell and turn the Anacondrai Cultists—including Skylor and Garmadon—into Anacondrai. Garmadon assured a sad Lloyd he was still on his side as Chen's forces soon overpowered the Elemental Masters with sheer strength, speed, and numbers causing them to retreat to the palace. While there, Garmadon was nearly attacked by Jay, who confused him for one of the Cultist, but Lloyd quickly explained it as Jay told Garmadon to pick a body and sticking with it. The Masters then watched as Chen's army escaped the island, leaving Garmadon and his young allies apparently stranded. However, Zane and Kai's success in summoning a Titanium Dragon and Elemental Fire Dragon inspired the others to overcome their fears summon forth their own Elemental Dragons, and they set out for Ninjago. Garmadon rode on Lloyd's Dragon and told the Masters a battle from the past had returned but stated they will rise to face off against it.
Flying back on Lloyd's Dragon, Garmadon and the others arrived back in New Ninjago City only to find that Chen's forces had yet to attack. Having their allies watch the city, the Ninja made their way to the Samurai X Cave where they were reunited with Wu and Misako, who was surprised at his appearance. Wu's pleasure at seeing him reminded Garmadon of his shameful secret, but they accompanied the Ninja to Kryptarium Prison to see Pythor. Chen's forces came looking for the snake as well, and a drop of Pythor's venom fell on Garmadon's hand, transforming it again as Zane realized that was why the Cultists came for Pythor: to maintain the transformation. Now aware of Chen's reason for not attacking, Garmadon, along with his brother and son, attempted to escape with the last true Anacondrai in tow. During this, the trio learned that Chen had lied to both sides during the Serpentine War. Unfortunately, they were confronted by more Cultists, resulting battle in which they lose Pythor to the Anacondrai Cultists and were forced to prepare for the inevitable invasion.
Back at the Samurai X Cave, Misako took note of Garmadon's sad look and grabbing his hand, she asked him about it as he attempted to tell his wife the truth about the letter but was interrupted with the power shutting off. Much to the horror of the allied heroes, the Anacondrai Cultists succeeded in luring the Elemental Masters away from New Ninjago City and various settlements, allowing them to invade unopposed. After Wu stated their fears have come true, Garmadon sadly remarked "The new Serpentine War has just begun."
The Destiny's Bounty 2.0 was soon in the air and Nya attempted to communicate with the Ninja, though Chen took control of the airwaves. Chen then told everyone about Garmadon's secret about his letter which was actually Wu's, infuriating Wu upon discovering that his brother claimed his letter as his own. Before a fight could break out, Skylor calmed Wu down before anyone could get hurt. He was reunited with Lloyd, who noticing Wu and Misako shunning him was because they found about the letter.
He is later seen on the Bounty at the cannons helping their allies take down the Anacondrai Cultists at the Corridor of Elders. Despite their efforts, Chen's army it through the path just as Lloyd appears on the ship with Pythor who tells in order to save Ninjago, Garmadon would need to be banished to the Cursed Realm so the Anacondrai Generals' spirits could curse Chen and his army. Garmadon willingly accepted this, feeling that he couldn't make up for all the evil he had done with what time he had left in his life. Wu and Misako were initially resistant, but in the end supported his choice having forgave him for his deceit while Lloyd was angered at his father's choice and left.
Wu recited the banishment spell as he tells his brother and wife to apologize to Lloyd for him but the latter appeared and accepting his father's reason finished the spell himself, banishing Garmadon and releasing the Anacondrai Generals who cursed and banished Chen and his army. Garmadon's likeness was then carved into the Corridor alongside those of the other fallen Elemental Masters.