Exorcism & House Blessings / Possessions

Exorcisms are a set of religious rites carried out when a person is possessed by a demon / devil. Most religious organisations have some type of formal rite used in the process. Christianity is the most well known, at least in Europe, though others like the following have it too: Judaism, Islam, Sinhalese & Tibetan Buddhism, Hinduism, and Taoism & Chinese Folk traditions. Many others do too though. A few religions see possession by spirits of any form as a blessing and only use exorcism as a necessity if the spirit refuses to leave.
Most will use religious symbols, holy water in some, religious texts involving the casting out of demons, and specially trained individuals to carry out the process. The type of demon depends on the religion, and for some like Islam it is Jinn, and sometimes in Asia it is as much ghosts & other such spirits that need exorcised.
In many cases the house, or other building, will be blessed to clear it of any negative forces, such as spirits, negative emotions or far fouler entities. In the Far East many nations carry out Feng Suey to align the house & it's contents with positive energy flows to cut down on negative aspects affecting the building. Either way, both are closely related, and if the entity is not fully banished or prevented from coming near the individual it could easily follow them no matter where they go.
A few speculate that any form of illness (whether physical or mental) is a form of possession, and needs help. This obviously by our standards today is generally not the truth. Yet many religious & medical procedures exist in tandem with exorcism being one of the most powerful remedies available.
Possession itself is a terrible condition. An entity generally latches on to a victim taking over their mind and dominating the personality. The victim won't eat, drink or sleep and will exhibit self harm in many instances. They will speak in tongues not known to the victim and have a hatred or fear of holy symbols. Levitation, dropping of temperatures, the victim's body is twisted & contorted by the host spirit. In many cases the spirit is usually a demon or devil belonging to the victim's religion, deliberately or accidentally summoned. Some are bound to a certain place waiting to pounce on unsuspecting victims. A few cases it is actually an aberration or undead spirit that takes control, and are easier to banish. Demons & devils generally aren't so easy, and may require more than one exorcist / exorcism. Most people are terrified of the prospect of it happening and avoid those that are.
In a few instances such as western African tribes that follow Voodoo, the practise of possession is strictly controlled during specific religious rites that allow the gods or their representatives into a host body. This is usually for a short period and allows the god and their worshippers to interact easier. Rarely if ever does a Celestial carry out a possession though it is unlikely due to the nature of these being to deliberately inflict harm unless forced too.

"We had to preform an exorcism on a Ms La Roshe, in Parisius. Horrifying it was. It took four strong men, holding a limb each to keep her from contorting and harming herself. She barely had the build to do it, but near broke free a few times. And the snarls, the language she spoke, and the swearing.... horrendous. And to think this was a 12 year old young woman.
Could barely show her the Crucifix or Rosary carried by the lead priest. Went insane with anger. Same if trying to say the Communion too. Every time she was presented with the Body or Blood of Our Lord, she vomited up a black stinking mass that smelled of saltpetre. And this went on for three or four days.
Eventually she calmed down somewhat, and she said the name Mammon. Turned out it was that foul demon inhabited her, and in her greed had invited him in to help her marry someone rich. In her way she didn't want anything less than a noble household and being married to a merchant wasn't to be. Hatred was what attracted Mammon and it took another three days to drive Mammon out. All this took was the constant ministrations of the exorcist and a visit from the Bishop of Notre Dame himself to add a spot of divine blessings to the procedure. Both took to blessing the house too, to make sure that Mammon could not come back again.
The one thing is that stuck out was the monster didn't want to leave initially until Ms La Roche was married to Burgomaster de Rais' son, who is also twelve at time of writing. We're going to have to keep a close eye on these two families as it appears no good is going to come of either."
Inq. Marc la Penne, member of the Ulmist Inquisition.