1. Who cut out Ethniu's eye?On that perfect bronze face, the mutilation of her eye stood out like a gallows in a public park. The orbital ridges around the socket were covered in white, granite-like scars, as if the biggest, ugliest cat you’d ever seen had scratched it out. It wasn’t sunken, though the lid was closed. That mangled eye bulged ever so slightly, as if it had been meant for a being considerably larger than she was.
Obviously would have to be something big, both literally and figuratively. It's our assumption that the Black Council are the ones who gave her the Eye, as it fits their M.O.
That being said, it could have been another group. Say, Tessa and Imariel and her more chaotic Denarians? They all love chaos and destruction. But also, what about the Outsiders themselves?
I could definitely see He Who Walks Behind having a role. He's been established as more than a demon, more than a hitman; he's a manipulator and a peer of Uriel. So he could definitely tear out the eye of a Goddess. He also could be large enough to leave such big scars. We have to remember that anything that could scar Titanic Bronze on a Titan is a serious being.
Another candidate is Lucifer himself. But why he would get that involved is harder to work out.
2. Is Ebenezar a Denarian?Hovering maybe twenty feet up, with his feet planted firmly on a stone the size of a Buick, was the Blackstaff, Ebenezar McCoy. One hand was spread out to one side for balance, fingers crooked in a mystic sign, sort of a kinetic shorthand for whatever spell was keeping that boulder in the air.
The other gripped his staff, carved with runes like mine, and they glowed with sullen red-orange energy. His face had twisted into a rictus of cold, hard fury. Flickers of static electricity played along the surface of the stone.
Now, it could just be about the amount of power in the staff that Ebenezar was putting into it. But. I seem to remember Harry's own runes on his staff used to glow the same color when using magic while he possessed a Coin. Considering how angry and barely controlled Ebenezar is...I could see a Denarian egging him along. One of the big things with Denarians is the reveal, the sucker punch. It would be quite the surprise to learn he is a Denarian.
The question is why? He already is a wizard, so he has power. He already wields the Blackstaff, so he already has a dark deal. Why get another? And when would he have done it? Why isn't he aiding the other Denarians?
Hard to say on any accounts. Perhaps, like Mab, he needs all the power he can get to do what he feels he has to. Cowl felt much the same. Simon even expressed sentiments of frustration on the limitations of being a wizard in the Paranet Papers. When he would have done it is impossible to tell, but I would guess it would have been before the Blackstaff was his (in this hypothetical scenario). And perhaps we just don't see him aid the other Denarians because it's all in the background. Or perhaps he is a rebel (along with his Fallen) and doesn't care to help the others. Or perhaps...he is leading the other Nemesis-infected beings, and he and his Fallen are in the same boat.