Hauntings

Many places, persons, and items are believed to be haunted. These cursed people, places etc, are as different as the races found on the earth. Each case is differs by what is causing the haunting, how it was created, and how to stop it. Many believe if a priest or cleric is trained or pious enough they can carry out a blessing or exorcism to get rid of the negativity.
Many items exist throughout time & space, and through the power used to create such products or where they reside, can easily drawn in powerful negative influences. Anything from a child's doll at the site of a mass murder, to a magical item being created using the darkest of spells & rituals, can easily be imbued with a spirit of some kind. This can range from the soul of the recently deceased, to an ancient spirit on an ancient item, to a demon or aspect of an evil entity. Most of these can radiant malice or other horrific feelings, also giving of nightmares, sights, and sounds that it should not. Some can also interact with the environment if it, or the invading spirit, has some type of locomotion. Many times it will make life a living hell for those who own it, who never suspect it as the cause of their problems. Sometimes only the destruction of the item, which is never easy, will stop the haunting.
Places that are haunted have a deep negative power tied deeply to what haunts it. Whether it is the site of a battlefield or graveyard, a necromantic or black magic ritual site, a house or building that a massacre took place, or other depraved deed, any number of things can set it off. All it takes is for even one truly evil being to die in a home that ends up still in use in some form or fashion and the place could be haunted indefinitely waiting for the next victim to come in. Sometimes a portal to a plane like the Shadowfell or a Hellscape is situated somewhere on the site and all manner of evil could come through. A few are built with the idea of trapping something in that should not normally be there. A number of rituals, like house blessings & Feng Suey, have been created over the millennia to offset at least some of these, though may only act as a temporary measure. If it is a demon, Jinn, or something similar it may even move with anyone who decides to leave. The area of the haunting is very oppressive, and seems darker & and the atmosphere heavier than it should be.
A person who is haunted seems to attract spirits and other creatures to them however infrequently. They have an affinity for them, a pure soul that attracts the opposite (looking to corrupt them), or dabbles or dabbled in forbidden knowledge & rites. They are either tormented by and/or possessed by these entities, whether just the once, by multiples, or multiple times over the days, weeks, or even years. They usually end up extremely sick, malnourished, and having a deep hatred of the world around them, especially towards established religious & social norms. They nearly always require exorcism to banish the entity. If it is a spirit or ghost, then it goes away, but if demons are involved them it may return at some point, requiring a further exorcism.