Source: In Search of Sanity, pg(s). 88-89
Oneirogens appear as figures cloaked in a strange, unnatural haze.
Oneirogens can be created from any humanoid race, when potent magic, such as those detailed in the notorious tome The Chain of Nights, attempt to tamper with the boundary between the Material Plane and the Dimension of Dreams. Careless usage of such magic risks transforming the caster or recipients into oneirogens. The pinprick-sized planar rift within their body destroyed their identity and erased their grasp on reality, leaving behind a husk, a slave to unchecked planar might, concerned with self-preservation above all.
The portals within most oneirogens lead to the Dimension of Dreams. Other destinations include:
- Abaddon (specifically Apollyon's realm of Plaguemere)
- The Abyss
- An Elemental Plane
- Negative Energy Plane
- Positive Energy Plane
- Shadow Plane
In the rarest case, the portal might wildly lash through the planes, constantly changing its destination. The effects of the planar energy that streams from an oneirogen depend on the portal's destination.
When many oneirogens are concentrated in a single place, the resulting flood of planar energy might cause unpredictable effects that are often deadly to others.