The edimmu were a type of utukku (a type of spirit or demon that could be either benevolent or evil) in Sumerian mythology and were envisioned as the ghosts of those who were not buried properly.
They were considered vengeful toward the living and might possess people if they did not respect certain taboos, such as the prohibition against eating ox meat. They were thought to cause disease and inspire criminal behavior in the living, but could sometimes be appeased by funeral repasts or libations.
The edimmu were also thought to be completely or nearly incorporeal "wind" spirits that sucked the life out of the susceptible and the sleeping (most commonly the young).
Edimmu in Order of Ecclesia is represented as a large sea creature, very similar in appearance to an oarfish, an eel-like fish whose some species grow to measure 11 m (36 ft) in length.
The Edimmu is a strange looking creature with the appearance of an eel, with a series of tendrils running along the top and bottom of it and two pairs of eyestalks. They will poison Shanoa upon contact.
It can be killed rather easily, though, but due to its aquatic nature, it is resistant to Ice attacks (e.g.: Grando); for this same reason, it is vulnerable to Lightning ones, such as Fulgur. It is also weak to Slash attacks, such as Secare.
Interestingly enough, it can be killed instantly if the player manages to decapitate it. That means that the player must focus their attacks on the "neck" of the creature in order to separate the head from the body.