Tom finds himself facing and losing to an increased number of UnderWorld deck players, so he decides to use an UnderWorld deck of his own. Kaz is thrilled and decides to help him out until his friend ends up on a hot winning streak without his help. Thinking that his friend will end up as a better UnderWorld player, Kaz secretly tries to convince Tom to turn back to his Overworlders.

During a scan quest, Peyton and Sarah encounter the biggest fighter they've ever seen. Kaz, Tom, Sarah and Peyton decide to track down the giant. But trouble comes for Kaz he bumps into a little creature called Hammerdoom Chantcaller who challenges Kaz to the coliseum and he has to battle or be banished from the Underworld.

Peyton is shocked to learn that he is battling the lead singer of his favorite band, and is offered free tickets to the next concert if he can win.

While exploring Fear Valley, Kaz runs into Chaor training four UnderWorlders in his latest attack on the OverWorlders.

Chaor's mission into OverWorld territory is threatened when Maxxor finds out about his scheme.

Peyton is beaten by Kaz and wishes to make the ultimate Drome match, but Sarah drags Kaz to Mount Pillar instead to locate a Danian BattleGear called the Mandiblor Crown as a way to repay her for obtaining a scan of Geltod. Meanwhile, Peyton and Tom face off in a match with 105 creatures on each side. Both of them get tired and sleep at the end.

Tom and company explore a giant temple for treasures to scan and discover much more than they bargained for. When one of the defense mechanisms mesmerizes Tom into a deadly trap, the rest of the gang (along with Larina) try to save him and Blazier.

Battling in the Crellan Drome, Peyton faces his most fearsome foe ever -- a huge Creature with a titanic temper and pulverizing powers, known as a Mipedian Warbeast. A player named Connor, with help from Klay and Krystella, tricks Peyton into trading 20 of his cards for a scan of the Mipedian Warbeast Blazvatan.

An unusual UnderWorld Creature named Phelphor is found frozen inside Ice Pillar by UnderWorlders. In the castle, Chaor, Agitos, and Takinom are amazed by Phelphor's tale of a lost tribe called M’arrillians and their discovery of the Cothica, Perim's greatest treasure, which they hold behind the Doors of the Deep Mines. Chaor states they will discuss opening the Doors to retrieve the Cothica.

Chaor and Lord Van Bloot's armies fight, with Chaor going after Phelphor. Phelphor mind controls the guards into opening the Doors of the Deep Mines first, letting out a flood of murky brown water that washes away everything in its path. Tom, Kaz, Peyton and Sarah scan the door as it opens but are forced to port to keep from being washed away.

During a high-risk scan quest, Tom Majors meets another Player named Tom and is dismayed to discover his namesake is taller, faster, and cooler. When CoolTom starts stealing his friends, he gets jealous and challenges him to a Chaotic match.

Tom promises to save the creatures of Prexxor Chasm from the disease ravaging them. Tom, Kaz, Peyton, and Sarah stop by Lake Morn to see its caretaker Garv, who may be able to help if he gets a sample of the disease.

When Kaz and Peyton are at the Lava Pond to obtain a scan of Zapetur, they are attacked by the M'arrillian Milla'iin, who is doing mysterious work with a hypnotized Khybon. Tom, Kaz and Peyton battle for the attention of a beautiful newbie named Shinwan who exhibits her skill in the Battledome by defeating Klay in her first ever drome match.

Tom, Kaz, and Peyton reach Broken Edge in hopes to find new Mugic and BattleGear for Tom's Drome Match.

H'earring leads Kaz to where Milla'iin was last sighted but ends up taken over by his mind control. Meanwhile, Tom is constantly bugged by Evan to battle Tom's Maxxor. Tom is informed by Sarah and Peyton he is an UnderWorld Player and Tom finds Milla'iin on his team.

Sarah and Kaz head to Ulmar's lab to get a scan for the Reality Field Generator. Peyton gets a call from CodeMaster Hotekk who would like Peyton to become his apprentice if he can prove himself worthy getting scans from Psikoom City.

After writing a school essay about how Chaotic is a real place, Kaz is sent to a psychologist by his worried mother. If Kaz can't prove he's telling the truth about Chaotic, his mother will take his scanner away.

Raznus, having been assimilated into the Danian Tribe, returns to Kiru City with Danian warriors. They are accidentally discovered underneath Bodal's arsenal and capture Tom, Bodal, and Olkiex. Odu-Bathax decides to raid Kiru City so Kaz runs off to get Maxxor, only for Intress to tell Kaz Maxxor is in the Riverlands.

Sarah is kidnapped by a ghostly Mipedian creature when she and Peyton are on a scan quest. Sobtjek and the other Mipedians learn the M'arrillians have flooded Ropa'Sahhk Desert where the Conjurers live from one of them, Scara. Scara advises they need to join forces with the Warriors of Owayki and Sobtjek takes a squad there.

During Kaz's second attempt to rescue H'earring, Chaor and the UnderWorlders plan to ambush the M'arrillians in a fiery trap involving Ulmar's Annihilizer near the oil-filled Marsh of Murk. Kaz ends up mind-controlled and Tom tries to rescue him while Sarah and Peyton look for a new battlegear called a Mindbander that can negate the hypnosis.

Tangath Toborn and his fellow OverWorlders must form an army from the Danians and the Mipedians. Meanwhile, Tom, Sarah, and Kaz go up against Peyton in a training drome match against Peyton's Erak'tabb. During the training, the OverWorlders, Danians, and Mipedians encounter Lystone who ended up controlled by the M'arrillians. After she is stopped, Tangath Toborn continues to train them.

The Codemasters initiate an emergency order to recall all Chaotic Players and shut down the Transport Systems as Perim is too dangerous with the M'arrillians about to conquer it. While Tangath Toborn leads a group to Glacier Plains to attack the M'arrillian base there trying to melt the glacier and flood the Overworld, Phelphor's army surrounds Kiru City.

The three go to Kiru City, where Najarin tells them he suspects Tartarek is a traitor to the alliance. Kaz, still in Chaotic, battles Tartawrecker to try to find proof. In M'arr, Chaor rescues Maxxor, they set aside their differences to capture Aa'une and succeed in taking him to Lake Blakeer.

With his powers enhanced from Lake Blakeer, Aa'une unleashes a devastating mindwave that races across the Overworld and reaches Kiru City, where the Tribal Allies watch in horror.

It's good news/bad news time for Chaor. The good news: Ulmar's brand new giant robots are bigger and badder than ever. The bad news: they're totally out of control!