The Defenders' secret training is interrupted when an earthquake signals that the monstrously evil Megalith is breaking free. Their mentor, Professor Alnar, reveals to them that their training will not be completed. They must immediately embark on a dangerous mission to re-imprison the Megalith by recovering the four Pure Stones.

On their way to the Monastery of Amos-Yan to recover The Key, a device that will lead them to the four pure stones, the group is ambushed by a band of thieves. The inexperienced Defenders find themselves trapped and only escape with the aid of the roguish and mysterious Adam. Seth is skeptical of this mysterious newcomer and suspects he's a thief as well, driving him away. Meanwhile, agents of the dreaded Order of Infinis, an evil organization intent on the release of the Megalith, arrive at the monastery ahead of the Defenders and ransack the place.

The Monastery burns as Malco and Flinch tear it apart looking for The Key. With the help of a bizarre creature, the Defenders sneak into the monastery and split up to find the Key. Meanwhile, Adam runs into the beasts from earlier and requests that they give him back the Nova Stone. Seth and Kara find the Elder Priestess of the monastery, who leads them to the Key.

While travelling with Adam, Seth becomes annoyed at him and challenges him to a duel. While they're away Mel, Eric, and Kara are attacked by a bounty hunter, Snare.

The Defenders come across a carnival. The circus misfits end up controlling Erik through an amulet. Mel goes to investigate and it turns out that both the circus members and Erik are being controlled by another creature.

For the first time in their lives, the Defenders find themselves on the high seas, where they discover that their Di-Gata stones don't work over water. When bandits attack the ship they are traveling on, their friendly captain proves to be more than he appears. Kara almost drowns twice, and Mel shows her Wizard of Yan powers for the first time.

A walled city held in the grasp of a ruthless dictator has a dark secret: its own citizens are being used as energy for the General Hod's crazed ambitions. For Kara, the situation becomes personal when her Guardian, V-Moth, is taken prisoner.

Seth learns the hard way that looks can be deceiving when the attentions of a pretty girl lead the Defenders to face destruction in a village where, literally, nothing is as it seems.

Deep in the bowels of an abandoned mine, the Defenders uncover a secret destined to shake the entire realm of Rados to its foundations: The existence of a Ninth Sigil. And it doesn't take long before the evil Lord Nazmul sends his agents Malco and Flinch to claim it for the Order of Infinis. Worse than that, Kara's boots start to act up and wishes she was not so helpless and that the Di-Gata Defenders would stop treating her like a baby.

The Defenders try to find a place to rest for a while but everyone they encounter slams their doors in their faces. They decide to camp at an oasis, where they spot a supply convoy in need of an escort just ahead. Seth refuses to help, however, as he is sure they will be turned away again. Meanwhile, a group of bandits plots to attack the same convoy. The next morning the Defenders find the convoy demolished and follow the tracks to a nearby village, where the citizens insist that they were to blame for the recent rash of robberies. A young Stone-caster named Kid Cole and his gang, actually the real culprits, arrive and chase them out, capturing Mel in the process.

Deep inside a mountain at the roof of the world, the Defenders encounter Brim, the original carver of the pure stones, now living in self-imposed exile and under siege by evil creatures, the Gisli.

The Defenders close in on the first pure stone. Their quest takes them to a remote jungle village where Erik is hailed as a Shaman, thereby making him an enemy of the tribe's medicine man. As they try to gain information from the tribe about the pure stone, the defenders run into Malco and Flinch.

The Defenders find the way to the pure stone, and eventually find themselves in a maze. Mel sees the pure stone and picks it up, only to have it practically take over her body. But when the others find her, the Dakonauts (Lord Nazmul's unstoppable robotic army) attack them.

Mel and Erik have eluded their Sand Nomad pursuers and are hiding out while Mel recuperates. Seth has struck a deal with Doku, a former member of the Order of Infinis, who promises him the location of Nazmul's secret keep in exchange for Seth's word that he will destroy Brakus.

On the run from Malco and Flinch and the Sand Nomads who have overrun the Dojo, Mel and Erik encounter Bo, a brash young boy who tells them of a warrior cult competition being held in a nearby county. They quickly realize the trophy is nothing other than one of the prized pure stones.

Mel dreams of a long lost monastery and a pure stone hidden there. Nazmul is able to read her dream and decides that it is Mel whose body he must have as the host for his incorporeal being. He dispatches Malco and Flinch to kidnap Mel, unaware that Brackus has stolen Nazmul's key and has gone to the monastery for his own purpose.

Adam charms his way into the Defenders’ encampment only to steal away in the night with their pure stone. His trail leads the Defenders to a den of thieves where an arms auction is being held with the pure stone as the main attraction.

While heading for the legendary Nexus, a traditional place of healing, the young heroes meet Raald who claims to be a Defender escaped from Brackus' dungeons.

On their way to the Pinnacle, the Defenders face the Obelisks, an army of war machines created for Nazmul by Flinch. Erik and Kara stay behind to try to stop the destruction while Seth and Mel head for the Pinnacle to hopefully cure Mel of her wizard attacks. At the Pinnacle, Seth must face Omniaxor, his father’s Guardian.

The Defenders discover The Machine of Binding and Erik devises a plan to re-wire the machine to enable it to draw the pure stones to it. Flinch and Malco attack them, while a strange metamorphosis is taking place within Seth.

Nazmul's secret quest for immortality brings his subordinates to an underground palace which once housed an ancient King who is rumored to have achieved eternal life. The Defenders arrive at the palace looking for Kara, who has been taken by someone.

Seth deserts the Defenders and head towards a Dojo to get an advice from professor Alnar about his condition. While looking for him, the Defenders stop to help a caravan of refugees fleeing the countryside directed to the safe village of Arboth.

The Defenders locate the Yin pure stone in the sacred floating city of Callisto but the presence of an invincible Guardian makes the mission almost impossible. The Defenders learn that only the Nova Stone would help them, but this stone is not in their possession.

In a surprise turn of events, Adam shows up at Brackus’ safe house with the four pure stones and Kara all tied up. Kara is grabbed and prepared for the host body transfer that will give Nazmul physical form. The Defenders prepare for the assault on the castle.

Brackus controls the Yintos Army and his only goal is to release the Megalith. The Defenders ask for Professor Alnar's advice about their mission true consequences, then they head towards the Place of Binding. Now the final battle for control of RaDos rages on.

With the Order of Infinis shattered and the Magalith released from his prison the Defenders head to a nearby farm to recharge their stones while Seth stays to see what they're up against. Not too far from there a young boy observes the scene.