Onereidoi

Onereidoi (sing. onereidoa, adj. onereidic) are the second-rarest and most magically influenced race on Esaethys. They take on a wide variety of forms, ranging from slightly strange looking humanoids to inhuman beasts to amorphous monstrosities. Likewise, their mentality varies from human-level to animalistic. All onereidoi have several traits in common, however, as well as a common origin.

Traits
Onereidoi are physical beings sustained and formed by the raw energy of the Will, shaped by a strong mental imprint. As such, they have no need for air, food, or water, though they often retain a desire for these things. In addition, they are extremely difficult to kill, as the primary factor keeping them alive is the strength of their magical imprint, not their actual metabolism. This also means they are mostly immune to direct magical attack, though the effects of magic can still harm them.

Apart from these traits, onereidoi vary widely. A majority are animalistic in form and mentality, while some are more humanoid, but have atavistic physical and mental traits.

Reproduction
Onereidoi are not born or made; they form when a mental imprint in the Will "leaks" into the mind of a magically powerful human. This imprint will first appear to them in their dreams, as a recurring motif, character, or monster. Eventually the dreams will become more vivid and common, until the imprint begins to manifest itself in reality. At this point the victim has irreversibly changed into an onereidoa, and will manifest some external feature of the imprint.

From this point onward, their form shifts in response to their mental state, with well-composed onereidoi being able to mostly pass as human. The formation of bestial onereidoi is a result of a downward spiral of depression and self-hate as the victim manifests more and more "monstrous" characteristics, eventually resulting in a complete and permanent transformation and loss of the self.

The cause of these imprints is not known to humans, but they become more common in the months surrounding a midsummer transit. Certain locations and in the proximity of other onereidoi are also believed to cause the change, but this is not confirmed.