Chaos Gamma (E-102ガンマ E - 102 ganma, lit. "E-102 Gamma") is a antagonist(later turned to a protagonist) in Sonic Battle. He is a robot created by Dr. Eggman and served as the doctor's principal robotic enforcer during his operations to control Emerl. During his service of Eggman, Chaos Gamma made numerous attempts to capture Emerl for his master. Chaos Gamma is unlocked in Sonic Battle by beating him in story mode, but he is not a playable character in story mode himself.

In Sonic Battle

According to Rouge the Bat, Chaos Gamma was constructed by Dr. Eggman as a part of the doctor's experiments using Chaos Emeralds on robot cores as power sources for his combat mechs. In these experiments, Dr. Eggman used parts from older or destroyed robots to create guinea pigs for his experiments. Chaos Gamma himself was created as a part of this robot line, presumably from the salvaged remains of E-102 Gamma, who was blown up on the first Egg Carrier. His robot line however was shortly postponed for the activation of the robot Emerl, an act that would play part later on.

During Dr. Eggman's experiments with the Emerl in Sonic Battle, the doctor implanted a whole Chaos Emerald into the Gizoid. Learning of this act, Chaos Gamma developed a deep sense of resentment and jealousy towards the Gizoid, as Chaos Gamma believed that the Chaos Emerald should have gone to him, and blamed the Gizoid for stealing the emerald and its power from him. When Dr. Eggman learned that the Gizoid had been activated, after he had thrown it out, the doctor deployed Chaos Gamma to retrieve the Gizoid, now named Emerl, from Sonic the Hedgehog and his friends. Thus began Chaos Gamma a quest to not only complete his master's mission, but also to take revenge on Emerl.

Chaos Gamma first appeared before Emerl, when Sonic and Tails were heading to Knuckles to get a Chaos Emerald from him. Chaos Gamma was initially mistaken by Sonic and Tails as E-102 Gamma, but the robot quickly revealed his true colors as he moved in to capture Emerl. Despite having his recovery mode restore his power once, Chaos Gamma was defeated by Sonic, Tails and Emerl, and he retreated.

When Tails and Emerl later came to Knuckles from Central City, Chaos Gamma tried to intercept the trio at the nearby bridge, where he engaged them in battle. After the first round, Tails tried to ask him if he was E-102 Gamma, but Chaos Gamma ignored Tails' question, before restoring himself and began fighting again. Eventually, Chaos Gamma was held back by Knuckles alone, allowing Tails and Emerl to escape.

Chaos Gamma eventually managed to escape Knuckles, and later located Emerl again, this time with Rouge, who had just kidnapped Emerl and was taken taking him to Club Rouge. Upon seeing Emerl, Chaos Gamma, who Rouge mistook him for a Guard Robo resembling Omega, entered his battle mode and began fighting the pair, but was defeated and was forced to retreat.

Some time later, Chaos Gamma found Emerl with Knuckles, who were heading to Night Babylon to find one of the E-121 Phi robots. Chaos Gamma ignored Knuckles as he questioned the robot, and began fighting the duo, but was defeated. Chaos Gamma managed to recover, however, and began a second round with Knuckles and Emerl, but was defeated again, and ran away as he once again failed his mission. As Knuckles and Emerl later made their way to the Gimme Shelter, Chaos Gamma was promised a whole Chaos Emerald from Dr. Eggman if he managed to take care of Knuckles and Emerl once they arrived, and Chaos Gamma more than willingly accepted the offer. When Knuckles and Emerl finally arrived, the doctor managed to trap Knuckles and then sent Chaos Gamma to finish them while he escaped. Now more determined than ever, Chaos Gamma pushed his power out-put beyond his limits and began fighting Emerl, but was defeated by the Gizoid. Chaos Gamma however, refused to be defeated and pushed himself even further, but was defeated by Emerl once more. After the fight, Chaos Gamma's energy source was too drained to continue battling, and he left the duo.

Despite suffering continuous defeats, Chaos Gamma continued to hunt down Emerl. He eventually located Emerl with Amy Rose, and Amy mistook Chaos Gamma for her old rescuer E-102 Gamma. Chaos Gamma then moved in to attack, but Amy then asked confused him if he was E-102 Gamma, to which Chaos Gamma replied that his memory did not contain that name and that he was not E-102 Gamma. Chaos Gamma then began fighting Amy and Emerl, but was left defeated and unable to fight any more, thus forcing Chaos Gamma into retreat.

Around the time when Cream, Cheese and Emerl were kidnapped by Dr. Eggman and were held captives in the Gimme Shelter, Chaos Gamma was given an Emerald Shard by Eggman to increase his power. While patrolling the shelter, Chaos Gamma was surprised when he ran into Cream, Cheese and Emerl, who were trying to escape through the ducts. Upon their introduction, Chaos Gamma promised Emerl that things would be different now that he had an Emerald Shard and that he would use it to crush Emerl and take his Chaos Emeralds. Letting out all his boiled up emotions, Chaos Gamma began pummeling Emerl in sadistic delight, while Emerl refused to fight as he did not want Cream to cry over the violence in a fight. As Chaos Gamma finally prepared to destroy Emerl, however, Cream and Cheese told Chaos Gamma to back off, but Chaos Gamma arrogantly asked what they could do to stop him and they began fighting. Despite Cream and Cheese putting up a good fight, Chaos Gamma easily recovered from the damage they inflicted. As he recovered, however, Cream, Cheese and Emerl managed to run away. Chaos Gamma chose not to chase after them, however, as he knew the ducts were the only way out, and waited for them to return.

True enough, Cream, Cheese and Emerl soon returned, now all three ready to fight, and Chaos Gamma promised vengefully that he would take Emerl's Chaos Emeralds from him, like what he believed Emerl did to him. Chaos Gamma was defeated in the insuring battle, but he absolutely refused to be defeated again. Restoring himself and pushing his power to its maximum, Chaos Gamma called upon a Guard Robo to aid him, but was defeated once more. After the battle, Chaos Gamma stood by and could not understand why he kept losing. Cream then asked Chaos Gamma what he was fighting for, and Chaos Gamma expressed his bitterness and jealously at Emerl for stealing his intended shard. Cream, however, reasoned with the robot, telling him that power was something you used to help those dear to you, and, after some long thoughts, Chaos Gamma found his shard being passed onto Emerl.

After these events, Chaos Gamma still wanted to destroy Emerl, and later found him with Shadow. Having been told by Eggman that Shadow was the enemy as well, Chaos Gamma tried to destroy them both, but was defeated. Chaos Gamma could not understand how he could lose as he had even managed to possess an Emerald Shard and tried to fight resume his fight with Shadow and Emerl, but was defeated once more. After the battle, Chaos Gamma was left so damaged that he could not move and began to malfunction. Shadow and Emerl then left Chaos Gamma lying in the streets, where he continuously repeated "destroy", while Emerl pitied Chaos Gamma's fate, which was the price he had to pay for serving as a weapon of Eggman.

After that, Chaos Gamma was repaired, and seemingly relinquished his grudge against Emerl. He then remained in Gimme Shelter where he offered to be a friendly sparring partner for Emerl before he went to stop the Final Egg Blaster, though it remains unclear why Chaos Gamma was doing this.