One issue I have always had with traditional D&D is that
idea that you get rid of a ghost by beating it to death with a special sword,
or blowing it up with magic. This is completely absurd, aesthetically very
difficult to visualise and it undermines the fantastic opportunity for
adventure and role-play represented by the haunting or possession. Characters
should contact the spirit and appease it, or force it out using their powers,
rather than simply kick the shit into it like they would any other Tom, Dick
and Hobgoblin.Hauntings
Hauntings can surround an object, building or individual that your PCs can encounter. The existence of a Haunting can be made obvious by the usual horror-movie fare: apparitions, unexplainable phenomena, and a sense that something is wrong. You should plan the backstory of the haunting in advance and cede clues throughout an adventure location. A good structure would involve finding the backstory through a mix of social encounters and discovery or contact with the haunting. For example, if this is a ghost of a jilted woman, why was she jilted? How did she die? What could she possibly want now? Give several means of laying the ghost to rest or allow players to invent one from the pieces in place (“Yes, and...” works wonderfully for this sort of quest.) The use of a maguffin or action should appease the ghost, and allow them to move on. Award XP as though solving an equivalent difficulty combat encounter.
Possession
In my The Last Day Dawned setting, there are two kinds of possession. There are victims of possession, and there are Willing Vessels. Willing Vessels are those who have entered into a partnership with a fiend and accepted them as a tenant in return for power. Once the Willing Vessel dies, their soul will be consumed and the fiend will rise again, in full control of the body and free to do what it desires in the world. At this stage, the fiend can also be killed to return it to Hell – the original inhabitant of the body is gone. Willing Vessels otherwise act in accordance with their normal impulses. Victims will demonstrate utterly changed behaviour. Unknown to most who make this deal, and most likely unknown to your Player Characters, is the fiend can assume control of the Vessel at any time.
Player Characters may find possession more difficult to detect, and schizophrenia, depression or other mental illnesses could easily be mistaken for it. Adventure hooks could revolve around rumours that a major public figure is possessed, or help with the strange behaviour of a loved one, or a spree or murders in a vicinity. Detect Evil spells will show those who are possessed, although not the nature of the possession.
In my The Last Day Dawned setting, there are two kinds of possession. There are victims of possession, and there are Willing Vessels. Willing Vessels are those who have entered into a partnership with a fiend and accepted them as a tenant in return for power. Once the Willing Vessel dies, their soul will be consumed and the fiend will rise again, in full control of the body and free to do what it desires in the world. At this stage, the fiend can also be killed to return it to Hell – the original inhabitant of the body is gone. Willing Vessels otherwise act in accordance with their normal impulses. Victims will demonstrate utterly changed behaviour. Unknown to most who make this deal, and most likely unknown to your Player Characters, is the fiend can assume control of the Vessel at any time.
Player Characters may find possession more difficult to detect, and schizophrenia, depression or other mental illnesses could easily be mistaken for it. Adventure hooks could revolve around rumours that a major public figure is possessed, or help with the strange behaviour of a loved one, or a spree or murders in a vicinity. Detect Evil spells will show those who are possessed, although not the nature of the possession.
Demons and Devils will never go willingly, and cannot be
appeased like a Haunting. They need to be exorcised. As before, individuals,
objects and buildings can all be possessed – but they will fight back so much
harder than a Haunting. Possessed
individuals will need to be restrained and unable to cast spells or initiate
combat if an exorcism is going to be attempted.
Exorcism
In my The Last Day Dawned setting, exorcism can be attempted anyone with a level in Cleric, Warlock, Paladin or Druid. You can negotiate if you want to expand this to encompass Wizards or Rangers or Bards or even Barbarians with your players, but I like the idea that this is a specialist skill set granted to those who wield divine magic or are accustomed to dealing with spirits of some kind.
If your players cannot rid themselves of the spirit using the above methods, they can attempt an exorcism. This is a specialised Ritual and series of skill checks. The initial set-up should take an hour of in-game time, and then a Religion or Arcana check is made to bind the spirit. I would apply a three-successes-before-three-failures rule, and run this section like a combat. Base the DC on the power of the spirit - exorcising Asmodeus should be tougher than your bog-standard Incbus. Between attempts, the spirit should take Lair Actions on initiative 20, and attempt to possesses the exorcist (Will or Charisma save of appropriate DC, failure leads to temporary possession – I’d grant advantage if the players thought to cast Protection from Evil or Magic Circle or Spirit Guardians or anything that feels appropriate).
To prevent other PCs from becoming bored in what should be a tense scene, I would run aspects of this encounter like a combat: the curtains catch fire, the Cleric’s holy symbol becomes red hot and flies across the room and your players need to put it out without interrupting the ritual. The weather changes, the roof starts to collapse, the room becomes impossibly cold. Swarms of vermin or animate objects or the living dead could awaken and try to disrupt the ritual, and will need to be fought off by the players. The ghost may attempt to communicate with the players, allowing your charismatic skill monkey to convince it to go quietly. Try to think of something that fits the nature of the haunting or possession that represents the spirit fighting back. All characters not actually involved in the exorcism should always be responding to other challenges and actions by the spirit.
More complex hauntings (such as a whole castle) might require exorcisms in several places. Differentiate these by the spirit’s response and use of the scenery to fight the players. One the battlements, storms threaten the PCs and the gargoyle come to life to attack them. In the basement, the walls bleed and the wine sets ablaze, and parts of the ceiling start to fall down.
Successfully exorcising the spirit should grant experience like a combat encounter. Failing to exorcise a hostile spirit? A horrible, but appropriate complication, and the possible possession of the unlucky exorcist.
