Eidolons cannot really be thought of as beings. They are more like free-floating forms of Essence created by the Sephiroth of Hod that attach themselves to the Panoramas in the Periphery. They are benign parasites with no self-awareness that the dreamer’s subconscious shapes, allowing them to become actors in the dream.
These mindless entities may appear as a dream lover one night and a dark stalker representing some secret part of the dreamer the next night. Most nightmares are really just the Eidolons reacting to the dreamer’s subconscious. Eastern Traditions, like the Storm Dragons and the Red Lotus, teach their students to confront their nightmares to discover hidden things about themselves. They believe Eidolons are mirrors reflecting the dreamer’s True Self.
Eidolons are not self-aware. They have no thoughts, motivations, or desires. Usually . . .
Sometimes a person struggles with a particular issue for so many years that it becomes a recurring dream. Filling the same role in the same dream night after night can trigger something in an Eidolon that creates the possibility of self-awareness. It can suddenly achieve sentience and realizes that it has become part of another’s mind, a mind that is obviously not doing a very good job of running its life, else the mind would not continuously dream the same dream night after night. It usually does not take long for the Eidolon to realize that it could do a better of running it host’s life.
At this point the Eidolon and the host dreamer must make Resisted Willpower Tests. If the Eidolon fails and the dreamer succeeds, the Eidolon loses its self-awareness and once again becomes another actor in the dreamer’s Panorama. If they both succeed, both identities have control and a Resisted Willpower Test is required to see who is in control at any given moment. If the Eidolon succeeds and the dreamer fails, the dreamer’s identity becomes trapped in his own subconscious and the Eidolon controls the dreamer’s body.
When this happens, the Eidolon becomes a Dybbik, and it proceeds to take over the dreamer’s life, possibly changing it completely. For instance the Dybbik might stop drinking and treat its inherited family better or it might suddenly quit the job its host held and take a trip. The Dybbik’s attributes are the same and it has all the same memories and skills as before. Some of the Qualities and Drawbacks may differ, however.
For a period of days equal to the victim’s Essence Pool, any Gifted who can actually observe Essence patterns and succeeds at a Simple Perception Test can to tell that something is wrong with the Dybbik-controlled person. However, when that time has passed only actively using powers like Mindread or Insight on that person reveal anything strange about him. Confronting the Dybbik at that point becomes difficult, as it no longer remembers ever having been an Eidolon. The person thinks that he is just a normal Joe who finally made some positive changes in his life. Now, he is happy and enjoying life.
And, he no longer has those bad dreams like before.