Gaia is the goddess of the Earth. While the UnWorld was created from the T-5001's body, Earth was created from Gaia's. She was curled into a ball, floating in space, and she couldn't even take a shower. Thus, she was covered by dirt and sweat, which created the continents and oceans as we know them today. She would later turn evil and try to destroy the UnWorld.
Creation[]
Gaia was created by the Undefeatables to serve as a protector of all the planets in the UnUniverse. Each of the Undefeatables was supposed to watch over one of the many dimensions in the UnMultiverse, but there weren't enough of them. Thus, Gaia was created to watch over the third dimension. However, when they sent her into outer space, she became rather cold. She became so cold, in fact, that she had to curl into a ball to keep warm. She did not move for eons, not even to shower. As disgusting as this may sound, it led to the creation of Earth as we know it, with Gaia's dirt and sweat becoming the continents and oceans, respectively.
Becoming Evil[]
Eventually, Gaia was freed by Giygas and turned into an evil monster. She crossed dimensions to reach the UnWorld, where she promptly began to wreak havoc.
Gaia in her evil, monstrous form.
Nobody knew how to stop her except for Satoru Iwata, who noticed a similarity between her and many of the bosses in the shames he helped develop. Thus, he formulated a plan. He summoned Sonic and Mario, who normally hated each other, and told them to combine their forces. Mario used a Fire Flower to power up Sonic's Chaos Emeralds, creating a mystical artifact known as the Chaos Helmet. Since it was designed specifically for Sonic's head, only he could put it on. Thus, Sonic became Knight Sonic and defeated Gaia once and for all while Mario protected Satoru Iwata from being stepped on (even though Iwata would later dedicate an entire year of shames to Mario's BROTHER, Luigi). Knight Sonic flew--yes, flew--into Gaia's monstrous face and stabbed her forty eyes out. Thus, the UnWorld was saved.
Aftermath[]
As the battle progressed, Giygas had treated himself to the front-row seat, watching from above. He was enraged when Dark Gaia was killed, so he disappeared to find himself another minion, simply because he did not want to fight Knight Sonic himself.