Quote Originally Posted by Iscah View Post
the Exarch's plan simply failed, resulting in a stable time loop from their perspective – not that they would know about it, as all sign of the attempt would be wiped out along with the First itself.
No. If their plan could affect their own timeline, then the time where they made their time machine would cease to be, ergo, it had to go to a different timeline. If they had not written the short story, this would still be up in the air.

The proof that it's a different timeline all the way back to the beginning of time is literally what I just said. If the 8UC time machine could go back in time within the 8UC's timeline, that future would not exist, and the Crystal Tower would have faded from the face of The First once the 8th Umbral Calamity was made impossible.

I'll try to make it clearer.

If they could go back in time in the 8UC's timeline, then they could go back even further than just the 8UC's inciting event, and cause different outcomes. They could go back to before Black Rose was invented and stop its invention. There are many other possibilities, but I don't care to think of them at the moment, but do you understand?

The 8UC's Crystal Tower did not land in their past, because it could not. The short story made this the sort of time travel we are dealing with.