A Buidu [ ] (pl. Buiduri [ ]) is the spirit of a being that was not taken by a Sinicam after it passed away. They are essentially what we refer to as "ghosts". Some of them have an unfulfilled destiny to take care of and some were so anchored on Gaiga that they refused to come with the carriers of the dead.
Buiduri struggle to traverse to the Above, as the visit of a Sinicam is the only way of safely passing to the haven of Malada without losing yourself in the higher realms. Sometimes it is a task that is left incomplete which forces the person to remain chained on Gaiga after it should pass over into the afterlife.
Those chains can only be broken through exorcisms performed by very skilled magicians, as the pure will of a spirit is rarely willing to move away since this would mean for the Buidu to roam the world without any place to settle and never be able to come into any contact with anything until the Buidu fades away when no one remembers it anymore.
Buiduri are not necessarily visible to the usual eye. Aura reader can spot a Buidu within seconds and those who are open to the other worlds can also feel the presence of a Buidu. But for a normal person to really see a Buidu, special glasses, artifacts or amulets are required, since only then the mind of the said person is able to process the information. The powers gained by the transformation into a bodyless spirit usually has to be learned by the now disembodied consciousness, as its thoughts and feelings are now influencing the environment without the limitations a mortal body brings with it. in turn, however, they are not able to physically interact with the material world anymore, only their indirect influence remains.
A powerful Buidu might even be able to attach itself to an object and temporarily use it as a body, making interaction possible, but this usually results in the Buidu destroying itself by spending too much of its CaBa maintaining the connection of it with the object and fading out of existence. There are cases of strong Buiduri which took possession of entire houses until the specter was either destroyed or its final chain broken. Rarely a Buidu passes over to the haven but rather gets destroyed, which is why many governments are against those exorcisms.
There are even more creepy scenarios, some of them include incidents in which a Buidu took possession of no object but a person. Sometimes, these rare occurrences go completely unnoticed both the possessed person and their surrounding environment. It is only then when the anger of the Buidu grows overhand, that the person also grows angry and starts to behave in abnormal ways. In the even rarer cases, in which a possession was correctly detected, the person grew conscious of its unwanted companion that weakened it and fed on its lifeforce. Such events are mainly a part of the past, as inquisitors and other people tried to erase unwanted spiritual attachments by exorcising in manners that rather killed the possessed person instead of freeing the Buidu from the person. Some counties still have Inquisitors and go brutally against any form of possession, as they see a greater treat in it as it is.
Buiduri are usually creatures to be helped, instead of fought against and if a persn is able to see the Buiduri it should feel compelled to free the spirit from its chains and make the way for the haven, instead of annihilating its existence.