A jiwa setan is a spiritual being that manifests as a dark shadow, and like a shadow, it is two-dimensional. It only hunts during the twilight hours of dusk and dawn when the shadows are the longest. It lies quiescent the rest of the day, sleeping in the shadows of trees or buildings, and moving as the sun moves. Its main food source is strong positive emotion, such as joy or love. A jiwa setan prefers the joy of magic users, but will feast upon mundanes if necessary.
The victim on which a jiwa setan feeds experiences anhedonia (total lack of pleasure or happiness) for a period of 12 hours (or until the following dusk or dawn), but recurring feedings can render this a permanent condition. Victims of a jiwa setan often appear pale and somewhat listless, in addition to their compromised emotional state.
Jiwa setan tend to live solitary lives. They do not age, but they can die from starvation. They avoid bright lights, as they can be damaged or even destroyed by them. Jiwa setan reproduce asexually, by binary fission; when a jiwa setan grows too large to comfortably fit in the shadows, it will split into two creatures. This happens rarely, perhaps once every few decades.
There are no juvenile jiwa setan. The collective noun for a group of jiwa setan is a nightmare.
Jiwa setan live in the shadows of Solaris Province, as well as on the islands of the Caribbean Sea. They prefer areas that are naturally shady, but need to be close to humankind to feed.
It is difficult to accurately measure the size of a jiwa setan. They seem to be composed entirely of shadow, posses a shadow's flexibility, and are flat to the point of two dimensionality.
Jiwa setan feed on positive emotions, preferably strong ones from magi, but they will feed on mundanes if necessary.
There are rituals that allow magic users to control a jiwa setan, allowing its master to use it as a spy or even an assassin. Part of these rituals involve regular feeding of the jiwa setan on its master; careful balance must be taken so the master does not find themselves lost to their spiraling negative emotions.
As noted, the jiwa setan is vulnerable to bright lights, and spells that create this effect. Absolute darkness will also drive away the creature, should circumstances mean that extinguishing light sources is easier than creating them. Recurrent victims of the jiwa setan are very likely in a state of dehydration, having lost all motivation for self preservation, so rehydration is a first priority of care.