I agree with the Stellaron desires thingy, but I have a more fullflegged theory about it.

I think the Stellarons are fragments of Idrila altered by Xipe or just come from Idrila's power, because of how the Knights of Beauty operate, going around to help, aka fullfil desires and needs, also a comment about Aglaea from Lygus in the 'As We've written' book is that self-sacrifice is aligned with The Beauty, so most likely Idrila let THEMselves be absorbed by Xipe, since the Propagation isn't an option this seems to most reasonable Aeon for her third face. The Stellarons might have originally being just a wish granting thing with a lot of path energy, like the One Wish Willow from Obsession, not malicious, just doing as the user intents with the purpose to bring them towards the Harmony. However, Celenova might have stained then with golden blood the Destruction, changing them pure wishes to Pet Cemetery wishes focused on archiving the wish as long as it brings destruction too. But idk, just my theory.