One of my favorite pieces of lore from the game is The Metaphysika Mysterium, which says the following:
It is said that we should not sully our hands when combating the forces of the Void. My studies have been deemed heretical by my brothers, but the rewards have been invaluable. I have harnessed the same energies employed by the Outsider and his accused followers while avoiding their corruption.
This work implies that an Overseer somehow managed to acquire powers, while supposedly remaining true to.. Well, loathing the Outsider?
It goes on detailing the author's methods:
Indirection: As the unwholesome powers of the Outsider use living flesh as a conduit, we can avoid being tainted by using the flesh of others instead.
Containment: By using Channels and Barriers we can focus these Void energies in a raw state, shielding them from the perverse perspectives of the Outsider.
This, for me, is a very interesting piece of trivia. What if the Abbey accepted these kinds of studies, and more overseers began wielding powers similar to Corvo?
Let's say for the moment that the Abbey is facing an all out war with, for example, the Howlers, and it's going very bad for the Overseers. Wouldn't they, in all their desperation, turn to the Metaphysika Mysterium in order to level the playing field?
I don't know exactly what to make of all this, but I'll say one thing: Void-touched Overseers would be pretty damn cool to see.