Aesyrium are a new type of Ovaform that has only recently begun to appear. A sort of "ascended" Aeternalae who are flexible and potentially abstract in form and style, embracing the chaotic Third Realm much more than is traditional. The Touch of an Aesyrium varies from person to person, usually exposing their soon-to-be Anina to their inner nature. Quite possibly changing said ningen into whatever Ovaform they subconsciously see themselves as.
The exact origins of the Aesyrium, as well as how their evolution from an Aeternal occurs, are shrouded in mystery. And truth be told, not much is known about them. Yet what sets them apart from other Ovaforms is their lack of Rescension drive and the capacity for greater gender fluidity compared to other Ovaforms.