“We shall deliver you from slumber. Bless us with a new form, and cleanse us all. Aelleah” — Eschaton Prayer
This is the Eschaton prayer. If we assume the Eschaton function like a polytheistic religion, albeit a cult, we can likely safely assume they have other prayers as well.
This particular prayer has some in-game significance: What the Eschaton priests were doing already was releasing their gods (from other dimensions most likely) or on a level of the spiritual plane, evidenced by:
“We found our great god and his many servants. We relentlessly worshiped them, offering sacrifices in return for power.” -Eschaton Scribe Lo-Ya Ygllalau, VI of VII
While we do not know what specific (probably eldritch) god they originally worshipped (maybe Azathoth- in the fashion of monolatry), we do know that something The Shining Trapezohedron did released their gods. Perhaps TST originally masqueraded as their god, or Nyarlathotep could have once he had departed from “dropping off” The Shining Trapezohedron.
That being said, both the prayer, regular in-game lore, and the last corrupted flavor text reveal that the Eschaton Mother still felt a need to complete the ritual that would cleanse the world:
“And so Mother Ishaela Bha’gor started the Holy Ritual, which would free our deity and purge this world of its impurities.” -Eschaton Scribe Lo-Ya Ygllalau, VII of VII
The ritual was either going to kill them all or somehow cleanse them and literally give the Eschaton a new form, so the concept of eldritch angels might actually hold some weight here– if everything had been successful, maybe the Eschaton would have been turned into eldritch angels as a reward.
Considering the trifecta of Shining Trapezohedron’s instructions —> but he’s technically Nyarlathotep (who gifted them TST in the first place) —> who follows Azathoth’s orders… Why would the eldritch want to “cleanse the earth”, other than to simply get rid of humanity?
The ritual was interrupted, which ruined everything in this underground world and turned everyone into monsters. More information on the Eschaton’s religion would likely help shed more light on the Eschaton’s thoughts about their gods.