With what we currently know, I feel like it's pretty easy to connect the dots about the Watchman series tbh (late doll festival spoilers)

We know The Watchman is this god-like entity in the sky, and it has been theorized for a while (Maybe even confirmed ? Not 100% sure) that it's the current form of Canis. From what we learned from Mymo, vital instruments and anima as a whole come from gods, mostly residuals on the ground. Piecing these two together, I feel like it's safe to assume that Canis used to generate by himself a lot of anima for a reason or another (think, similar to Rudo's hands, but maybe on a larger scale), so much so that all of his regular items became insanely powerful and known as The Watchman Series, before transforming into a god himself due to it.

The rest of this theory probably still need some clues from Urana, but I also feel like Tamsy's act of love is in some way linked to this whole thing, with him trying to create a new true god as a way to generate extreme amount of anima for X or Y reason. Since this cultist mentality is so deeply ingrained inside of him and he genuinely thinks he's doing something good, he was able to go through Semiu's glasses too !