Aqua Magna (OU)
In the time before time, Aqua Magna was a huge ocean that covered approximately one third of the world of Spherus Magna. The Great Beings, rulers of Spherus Magna, became alerted to a threat to their world when they discovered that the spread of a destructive substance named Energized Protodermis deep beneath the surface was weakening the structural integrity of the planet, which meant that it would only be a matter of time before it split violently apart. Even with their vast creative intellect, the Great Beings were unable to envision a way to stop the spread of the EP without worsening the damage, so they instead put some alternate plans into motion. The first was the development of artificial atmospheric shells that would activate in the event of a cataclysm and maintain the criteria needed to support life so that the people of Spherus Magna could live on after the planet's destruction. The second was the construction of a massive, near-planet sized robot named Mata Nui that would depart Spherus Magna to research the other civilizations of the universe and return to meld Spherus Magna back into its original form.
In 80 CMT, Spherus Magna split into three planetoids: Aqua Magna, Bara Magna, and Bota Magna. The atmospheric shells that the Great Beings created were successful in stabilizing the planetoids and providing each with its own artificial atmosphere, complete with centers of gravity, weather cycles, and other features necessary to ensure the continued survival of the Spherus Magnan species on their new homeworlds. The shattering of Spherus Magna was given the obvious name of "The Shattering" both by its survivors and the Great Beings.
The Great Spirit Sleeps
At some point before 50,080 CMT, Mata Nui returned to the Solis Magna system but fell unconscious and crash-landed into Aqua Magna. The Red Star, a satellite that served as a booster system and repair station for Mata Nui's inhabitants, settled into Aqua Magna's orbit. Mata Nui's collision dislodged Voya Nui from its original location in the Matoran Universe and launched it through the outer hull to the surface of Aqua Magna, where it settled on the surface waters and became an independent island. The unconscious Mata Nui sank beneath the waves, but his face remained visible above the water, so the camouflage systems in his face created an island on top of it that, when discovered by Matoran Universe inhabitants, was named the "Island of Mata Nui" after the Great Spirit himself.
Despite the fact that the Matoran Universe was located underwater, it became the center of most of Aqua Magna's events because it contained most of the planet's inhabitants. Those that lived outside the Matoran Universe did so because they were either displaced against their will or they had just migrated to the surface islands of Mata Nui, Voya Nui, and Shinobi-Nui.
At an unknown point in time, the island of Mata Nui was destroyed.
At some point between 99,080 CMT and 100,060 CMT, Zev Raregroove travelled to the Green Belt of Voya Nui, but was followed by Blackout aboard the Nemesis. Blackout defeated several Hollows and proceeded to bomb the Green Belt out of existence with fusion bombs, which prompted Zev to rename it the "Grey Belt". Voya Nui was later completely destroyed in an unknown event, leaving Shinobi-Nui as the last remaining land mass on Aqua Magna.
In 100,080 CMT, Blackout discovered that Mata Nui was dying and the Matoran Universe was soon to become uninhabitable, so he brainwashed most of the Matoran and ordered them to dismantle as much of their surroundings as possible and use the resulting materials to build Darkmount. The completed Darkmount then departed Aqua Magna as Blackout's flagship in his crusade to conquer the rest of the galaxy while the remains of the Matoran Universe were left to rust.
In 150,080 CMT, Ynot commented that it was ironic that Blackout used to chase him to the ends of Aqua Magna trying to kill him, only for Ynot to end up chasing Blackout everywhere except Aqua Magna in the hopes of defeating him.