Yeists are one of the 6 types of PARA.
Yeists are unique among the PARA, as one becomes a Yeist not through biting, but through being inhabited by a yeist for a period of exactly one year. At the end of the year, the possessed body blinks out of existence, and both the possessed individual and the yeist possessing them get sent to their focii. This process is called Yeistification, or being "Haunted". Someone whose body is possessed with a yeist can be referred to as having a "Yeist Infection."
One becomes possessed by touching a focus which is possessed by a yeist. The yeist then gets transferred from the focus to the individual who touched it, and has complete control of their body. It generally takes a few weeks for the yeist to get the hang of controlling the new body.
- Yeist refers to the yeist both while they are inside the focus and while they are controlling a body which is not theirs.
- Polteryeist refers to the consciousness of the body while the yeist is in control.
- Host refers to the body which is being possessed by a yeist.
Destroying a Yeist
If the Host gets destroyed, so does the Polteryeist, while the Yeist is sent back to their focus. If the Yeist's focus is destroyed while they are possessing a body, then the Polteryeist gets control of their body (the former Host) back, with full magical ability. If the Polteryeist's focus is destroyed, the Yeist gets forced back to their own focus, while the Polteryeist gets control of their body (the former Host) again - however they are completely unable to use magic from then on.
Destroying a Yeist's focus is the most common way of permanently destroying a yeist, and believed by many to be the only way. There is also, however, an 8th level Healing spell which destroys a yeist if it is still in its focus. There is also a common 1st level knowledge spell which enables you to know whether or not there is a yeist contained in a focus, by making it glow according to the yeist's alignment, using the PARA Colour Chart.
All yeists are completely unable to do magic of any kind.
If a yeist's focus gets touched (while the yeist is still inside) by an animal, then the yeist gains control of that creature. However unless a spell translating the animal's speech is cast, then they are unable to be understood. Unlike human possession, when a Yeist possesses an animal, they are not blinked out of existence at the end of a year: rather, the possession goes on until the animal dies, generally from natural causes, fights with other animals, or the yeist tiring of controlling a beast and throwing it off a cliff.
As a rule, yeists are considered evil: a good or neutral yeist is likely to, as soon as they have control of a host, turn around and destroy their focus. It should be noted, however, that just because this is assumed to be the case, it is not always so.