Creation and Usage
Prior to Sonic Unleashed, Dr. Eggman learned of the existence of Dark Gaia. Seeing that this creature's limitless power could help him create Eggmanland and take over the world, Dr. Eggman sought out to harness this creature's power. With the information provided from the Gaia Manuscripts, Eggman figured out a way to awaken Dark Gaia from within the planet's core and constructed the Chaos Energy Cannon for this. Its function was to take the seven Chaos Emeralds and reverse their polarity, thereby creating a dark energy blast that would force Dark Gaia to awaken from its slumber.
For the Chaos Energy Cannon to work, however, Dr. Eggman needed the seven Chaos Emeralds, which was in the possession of Sonic the Hedgehog. The doctor then orchestrated a plot where he would launch a space armada of his Eggman Fleet and threaten to take over the world, with the purpose of luring Sonic and the Chaos Emeralds, which the doctor anticipated Sonic would use to turn into Super Sonic, into his Chaos Energy Cannon.
Dr. Eggman's plan proved successful, as Sonic arrived at his fleet and turned into Super Sonic. Having disguised his Chaos Energy Cannon as a space station, Dr. Eggman tricked Super Sonic into the center of the cannon, where he trapped him in an energy shield and robbed him of the Chaos Emeralds, thus completing his Chaos Energy Cannon and allowing him to awaken Dark Gaia.
In the end, the Chaos Energy Cannon was a one-sided success as it managed to awaken Dark Gaia, but also wielded some undesired results as well; even though it awoke Dark Gaia, the beast had not matured enough to awaken properly, and therefore broke apart and scattered across the world, leaving Dr. Eggman with the task of reconstructing it.
Additionally, the feedback created from the Chaos Energy Cannon caused some of Dark Gaia's energy to infect Sonic, giving him the ability to transform into Sonic the Werehog. The process also left the Chaos Emeralds drained of their power, which led to the doctor discarding them along with Sonic from the Chaos Energy Cannon. This later proved to be the doctor's undoing, as Sonic used them to reverse the Chaos Energy Cannon's work.
In Nintendo World, the Chaos Energy Cannon was constructed and attached to the Death Egg Mark II.