(warning fer manga spoilers)
My main gachiakuta theories are
A; the no man's lands are actually the sites of long dead gods, hence why they're so volatile and different.
B; Rudo has a god, or possibly the heart of the watchman itself (which might be the only god left) trapped/sealed inside him/his bloodline.
C; Regto and Tamsy were co-conspirators trying to restore said god to take down the Sphere fer good. (Personally believe Regto might've been Tamsy's past teacher/noble or family advisor etc who shared his plans fer the Sphere/Rudo to Tamsy as a child before purposefully getting himself exiled to the slums n killed, or was from the slums and befriended/radicalized Tamsy in secret meet ups.)
Oh and this is more headcanon or what I'd prefer to see, but D; Tamsy might have originally started with 'good' intentions, legitimately caring about the Ground, wanting to get justice, (an act of love for this place that he could be free) but got more and more twisted as he had to he put on a facade around both sides to accomplish his goals, ultimately losing himself and ability to be himself around others. Doesn't excuse what he's done but maybe, like Amo, he has a chance to course correct and actually help Rudo instead, or at least, stop what he's doing.
This isn't theory but smth to note;
Rudo, Tamsy, and Zodyl all want to take down the Sphere fer their own personal vengeance, not fer the people of the Ground itself. I hope we get to see more of Rudo interacting with the actual community of the Ground, not just the Cleaners. As the Cleaners themselves were never fully intended to protect the Ground's people in actuality as Corvus reveals (doesn't erase the good they've done and do, but it doesn't sit well with me. Do they help for free? Do they charge? Do they trade, as in, mutual aid? They seem to better off than the average Groundling and Towns) Otherwise, he'll never be able to meaningfully live a good life and have fun in contrast to the Tribesfolk's crab in a bucket mentality, if he doesn't connect with the normal people of the Ground more. The families, the neighbors, the labourers, the artisans, the scholars, the poor, the sick, etc.
I hope the Doll Fest changes that. Changes him fer the better and he can build real solidarity with. Then he can brutally take down the Sphere (and as much as i want him to go apeshit, chose not to kill the regular people of the Sphere bc at the end of the day, he's still a kid who doesn't need that on his conscious.) (I wont say anything if he kills any rich folk tho fuck em.)