Oni are a race of evil spirits native to the Material Plane.
While oni are incredibly varied in their shapes and powers, they still share certain traits in common.
- Regeneration: All oni regenerate, although the rate of regeneration varies. Damage from fire or acid can kill an oni.
- Change Shape: All oni are shapechangers, but their ability to change shape is generally limited to creatures similar in shape to their true form.
- Native: Oni are native outsiders. As evil spirits clad in mortal humanoid flesh, all oni also possess one of the humanoid subtypes—usually giant.
Oni are a race of evil spirits, native to the Material Plane, that manifest physical bodies based upon the shapes and desires of humanoid mortals. In pure spirit form, an oni is nothing but a disembodied evil longing for the sins of the flesh. In this form, oni are harmless and invisible. The majority of these bodiless oni were once kami who failed their wards, or more often, who deliberately abandoned them. As punishment, they were stripped of their ability to form a physical body and then cast into the void. Rarely, a mortal creature's soul can become a disembodied oni upon death, or in even rarer cases, after a truly evil individual has undergone a particularly vile ritual that ends in suicide. These oni are more often destined for positions of great power and strength than most. Eventually, an oni's spirit manifests a physical body on the Material Plane. The methods by which this may occur vary, but the process generally takes place in areas already despoiled by sin, tragedy, or cruelty. The type of oni a spirit transforms into is influenced by a wide variety of variables, ranging from the nature of what the oni spirit was before to the location where it is reborn into the realm of flesh and blood. Once an oni manifests its physical body, that body becomes its true form for the rest of its life—all oni are shapechangers, but this original form is the form in which they are born and the form they revert to upon death.
An oni's true form is always similar to that of a specific type of humanoid, save that it is always deformed and monstrous to look upon. Tusks, additional eyes, or strangely colored skin are common physical attributes. Yet while they have hideous forms, all oni are capable of changing their shape to assume forms more pleasant to the civilized eye. The type of shapes an oni can assume depend upon its species, but all can transform into some form of humanoid. Oni use this ability to infiltrate humanoid societies, either to prey upon the weak or to rule them in disguise.
In order to understand oni, it is important to consider that most of these beings were once spirits tasked with protecting a material realm they now believe is undeserving of such care and concern—indeed, the physical world is to be dominated and consumed. They arrive in physical form starved for sensory experience, and never fully sate their desire to gorge on such experiences. Most oni seek to attain positions of leadership and power, often in the guise of a normal humanoid, in order to secure a never-ending supply of sensory experiences. It is also important to understand that oni's immoderation is also motivated by their corrupted and evil natures—that is, no pleasure is more enjoyable than one that deprives or wounds another.