A loose thought in my head about our dear, sweet Lady Ethereal. Spoilers for Nine Sols ahead!
Okay. So. Eigong was definitely the one who did this, right?
If any of the Dusk Guardians could tell that Lady Ethereal had life support unhooked from her Vital Sanctum, at the very least they'd hook it back in, right? Bar that, they'd find a way to wake her up, right?? They'd have no reason to stick her in a jar, they're just here to work until they're discharged. So it wasn't them.
None of the nine sols had reason to do it.
Goumang had complicated plans to make her greenhouse adhere to, and while she knew that solarian brains could be used for the neural network, she didn't seem interested doing so.
I'd wager Yanlao has exactly zero knowledge about anatomy and biology, he was too busy kissing up to the rich.
Jiequan wouldn't have done it unless there was transmutational value in it, and though he probably would've found Lady E's suffering interesting, he probably wouldn't have gone with the jarred brain method.
Fuxi was dealing with Tianhuo, and Nuwa's a rich, traumatized brat who's more worried about her brother than anyone else.
Kuafu just straight up wouldn't do something like that.
In the final boss battle, Eigong has this to say to Yi.
She tried to trap Yi in her Soulscape. She was expecting it to last longer. She knew how to make her Soulscape something other than pleasant dreams and a gallery of memories.
I'm not saying this is concrete evidence. But it's something.
But why would she do that? Why would Eigong subject Lady Ethereal to an utter loss of autonomy and 500 years of horrifying nightmares? The whole thing's excessively cruel, even for her.
Maybe Lady Ethereal discovered something.
My thought is that Lady Ethereal caught a glimpse of the truth, and it was the straw that broke the camel's back. Not only were her colleagues and her beloved daughter dead, the system they died for was going to be used by the person that created the Tianhuo, that doomed solarian-kind.
So right before she put herself in her Vital Sanctum minus the life support, she sabotaged the Soulscape system, planning to die with its secrets.
But Eigong found her. Pried open her mind to find out how to fix it, and then made her a part of her life's work.
Made sure she didn't die, for good measure.