Stupid question

[Alenore]

This, and he talks about

A promise made

indicating a deal was made with her when he sent us back to Elpis

What's this promise? I haven't read anything about a promise in his monolog, only "Alas, I dare not investigate in earnest before the coming of my guiding star, as he foretold.".
"He" would not refer to Venat but someone else. Elidibus' unknown twin brother?
The fact he has a white robe means he was a public servant of some status who gave up his place (just like Venat), or Elidibus himself. Or perhaps, instead of destroying Eli's soul when he sent us back in time, it freed him and he played us.

Okay so I knew it was a stupid question because now I see how obvious it is.

Also...

...never even dreamed of thinking that Elpis is still around. I had this idea that the whole ancient world went to, you know, shit. So was it "only" amaurot?

Well it...

... is no longer around.
Elidibus says so when he mentions it : "Elpis itself would tell even less. Nary a ruin has survived─"
Except if there's some part of it that was sundered on the First or something, but I doubt meteors falling on the star + a calamity of wind + a calamity of thunder would fare well with floating islands, that apparently had to be regulated on a regular basis so its aether wouldn't go out of balance.

As for the ancient world itself, well, it's still around in the form of ruins in the Reflections since they didn't have to weather the calamities, but ruins nonetheless.