>>65
I agree with all your points.
I think the Pus of Man is the concentration of the Abyss in humanity. Some individuals have more of that concentration than others (or maybe just less humanity to offset the Abyss taking over?), and if it's not properly "taken care of", it will burst out of them once they're hollow enough.
It seems like Lothric is the place to be for these fellows, more specifically the Grand Archives of the Castle. I think the scholars there studied this and where able to transfigure Pus of Man into something greater. They may have worked with a Primordial Serpent to do this, as there are statues of them in the Archives area.
My theory is that the Butterflies are the "imperfect," or unfinished transformations, while the Angles are the more "prefect" transformations.
>Pilgrims do this ritually, just now Lothric is fugged.
>Lothric inhabitants have gotten so hollow, they start transforming.
>Depending on soul level they're either transformed into the Pus of Man creatures with the snakes on their back (symbol of imperfect dragon), or are transformed into a tree (low soul level).
>Some creatures like the Corvian Storytellers are "imperfect" souls who start transforming, but because of their tainted souls turn into what you see in game.
>The Winged Knights are on their way to a "perfect" transformation.