Thank you so much for asking this!! And I do have some head canons for Peach! I wish he would appear more in the game (through texts,books, and paintings.) it even just texts about living in pitch darkness underground. But I am not a chemist or a biologist! So all these are my thoughts and opinions.
People used to live in the ruins underground. To me it gives me Metro 2020 vibes on monsters and people living in isolation. But as more and more people struggled to even survive, it gave way for some individuals to want to venture into ‘forbidden’ areas in hope of saving themselves, loved ones and people.
But we need to talk about the 4 histories of my time at Portia.
Age of corruption. This time period is a bit further than where we are right now. We are almost living this life but normal civilians don’t access to human sized robots (Ack) to do our house chores just yet. But the age of corruption is just humans living lazy, luxurious, and pampered lives. Which unfortunately when you have humans that get whatever they want with very little effort it makes greed and entitlement a big problem.
Day of calamity - entitlement meant war. Consider it like nuclear war. Humans created weapons to conquer and destroy neighboring cities. The smoke from the chemicals, and fires covered the skies. Chemical rain caused mutations in animals creating some of the monsters we see in the game. But the chemical warfare didn’t just Mutate animals...it also affected humans. Between the war and chemicals the human popular became sparse. Now I don’t remember if the game mentioned exactly what the smoke was that covered the world but I can only guess it was the chemical smoke. Which goes into
The age of darkness. Humans lived underground. My guess is because of the chemical smoke clouds which meant chemical rainfall. (Chemical rainfall is a real thing even now. Our real world is so infested with pollution that it rains out of the sky 💀). So humans to escape the nuclear chemical infested air (okay technically it’s the dust particles but I’m gonna say air), water, and rain they had to live underground because the air would be unbareable for humans. I like to think of Fallout for this. Like in fallout 4 with nuclear rain and how it hurts and Being near radiated water hurts. But with the sun covered away for so long initiate a nuclear winter. So humans now living isolated underground would cause problems naturally... finding a mate would be hard being confined to what group your ancestor fled with. Plants don’t grow well without sunlight, radiation is in the water, lack of vitamin D, and no proper ventilation for smoke, FREEZING temperatures and the threat of other creatures that lived underground.
The age of darkness is when the church of light was formed. In times of panic and fear religion thrives. Stephen Kings the mist shows how fast religion can come about in times of fear, and uncertainty. Which would have split our already divided survivors. The religious followers who believed religion will save them and the explorers who didn’t beleive saving would magically happen.
This is where Peach would have been born. He would have been born underground and he was apart of the explorers. He aided in the dangerous ruin dives to find technology that was salvageable. I feel a lot of people would have died finding all this technology. Because I think peach wasn’t a fighter per say as he was more of a scientist. It would have taken the combined work of an explorer/adventurer and scientists to get it all going. But peach managed to build a machine to dispel the chemical induced darkness. Which lead to
The day of the bright sun! Peach used the machine to dispel the clouds in as many places as he could. But of course it took decades before the clouds fully disappeared. But even after humans were finally free...humans went right back to war again for control. But now control for the ruins and the technology within them.
That was a quick and not so great overview! But now my head canons!
💻I don’t think Peach lived a long life. He would have been exposed to radiation and chemicals during his entire time exploring for parts, building it together and having to go to the surface to use the machine in the first place. He probably died a painful death and the radiation slowly but surely killed him.
💻I don’t believe he would be a church of light follower. During the age of darkness the church believed all technology was evil. But Peach believed and risked his life every day to find technology that could save them.
💻I feel he’s a nerd and not a fighter. Django says after Peach, people formed the civil cops and military over knights. Which I think means civil corps were originally people who aided in the ruins dives to keep the scientists (Peach) safe.
💻he popularized umbrella hats because he used umbrella hats so he could use his hands while protecting him from the radiated rain.
💻now for how he neutralized it’s I’m not so sure. I presume it would be like Nagasaki and Hiroshima. They had to build on top of the city to get away from the radiation. Which makes sense as to why Portia is built on top of the previous city that it was 300 years prior. But I think maybe Peach built some form of a a reverse osmosis, carbon air filter, and some Ion exchange to purify the water. Hence why Peach is a total nerd. Because I don’t understand science so much XD.