Baronon was doing what he and his brothers had been doing for years now. Digging. On the Southern Continent, near the Tren Krom river, it was a very hard life. Resources were scarce. Metallic Protodermis especially. If they were so lucky as to find some, they would maybe get a few tools out of it. But oftentimes, they broke as many tools in the mines as they made them.
Even still, they had to continue. Mining was all they had, for when you are on the Southern Continent, there isn't much to do outside being killed by whatever Makuta, Dark Hunter, or Rahi you came across. Not helping was how weak everyone was. Everyone in Baronon's village was a product of Karzahni's handiwork.
However, while many did not know it, things would get far worse than they already were. For it was on that day that Baronon was Mining...that his faith in the Great Spirit would vanish entirely. For on that day, the great shadow fell, and Voya-Nui rose above the line of the sky. The resulting quake caused the life energy from the heart of the universe itself to flow into the waters all around. And so it mixed with the Tren Krom river, and said river flooded into the caves the Onu Matoran were mining in.
The now greenish water rushed in from all openings, quickly entering the systems of the Matoran inside. All were changed. Several were made taller and stronger, like before their alterations by Karzahni. Others were changed horribly. Becoming horrid, aquatic monsters, with now only an instinct to kill and destroy. But for Baronon, his shape remained the same. He was still small and weak. He was also drowning, the water entering his system extraordinarily fast, before he could get a truly good breath in.
The water inside him, though, began to disappear. It merged with him, on the inside, and Baronon felt stronger. Not physically, he was not changed in shape, but he found that he now had air in him, and that his body had an easier time swimming. And it was a good thing it did, for the monsters among his former friends began attacking and devouring the largest and closest of them. Baronon only barely made his way out of the cave, pursued by a being that now looks like part Takea shark.
He barely fit though a small opening, out of breath, exhausted, and gasping for air, trying to stay conscious.
When he awoke, he discovered that he had been changed in a way he could not imagine. His armor and organic components were all...blue.
As was his mask.
He was, for all intents and purposes, a Ga-Matoran.
He returned to his village, what was left of it. Amid the grieving and repairs, there was still enough in them all to mock and ridicule him, for some. For others, they merely shunned him and mourned the deaths of the others.
It was that way for years. And when Matoran began to forget about the tragedy, when they got over it, and found some semblance of normal life again, the shunning, and mocking, and laughing only intensified. And all that did for Baronon was annoy him, after a while. After a while, he began carrying an axe. A very large one. And for a long time. Baronon was left alone.