This is an idea that I just got to get down on paper, even if nobody likes it and is totally cliche. It's a mish-mash of various table-top games. See if you can spot the influence!
This would ideally be a one on one between a spirit(s) and a Medium. I'm not too picky about the role I take, but I wanna hammer out the setting first.
What are Mediums?
Mediums are a select group of people who are born, or who have developed a powerful spiritual energy called 'Wisp'. It's next to useless for normal humans, but it boosts the natural abilities of spiritual entities. Most Mediums use this energy to barter with spirits for favors or service.
Where do they come from?
In the past, most Mediums gained their Wisp through a strict training regime of meditation, exercise, fasting and some form of creative expression (like painting, writing, music, etc). These people were mystics and priests who kept the true reasons for their odd behavior a secret, explaining their actions as devotions to a particular religion. However, in the past 20 years there have been a large number of people that have been born Mediums with a good deal of spiritual power. They are not as skilled or as knowledgeable about their condition as trained Mediums, and tend to get into a lot more trouble.
Wisp to Humans
Wisp is a sort of radiation given off by a strong soul. It has little to no affect on the physical world, but people with strong souls seem to be full of life or energetic to others. Wisp can be given away to spirits or other humans. There are many rituals to transfer spiritual essence, but the most efficient and most common method is sex. With spirits, the first encounter is done telepathically or through dreams. The telepathic joining gives just enough Wisp for the spirit to materialize and continue the affair.
With enough practice, a Medium can turn his or her wisp into a weapon against incorporeal spirits, or give her better control over her body (like controlling breathing, heart rate, dealing with pain, etc). All Mediums can listen into the spirit world, no matter how strong they are.
What are Spirits?
Spirits are beings made of pure energy. Some spirits are the mirrors of an object, event, or group of objects in the material world. Trees, cars, storms, the sun, pollution, fire, and glass are examples of mirror spirits. Other spirits embody a feeling, concept, action or idea. Some examples are spirits of joy, fear, rage, competition, boredom, combat, beauty, righteous indignation, paradise, and justice.
These creatures exist on the astral plane, a spiritual mirror of our material world. They can see and hear into our world, but can barely influence it at all. Which kinda sucks, considering that their existence is tied to what happens to the object or concept that they embody. If the tree of an oak spirit gets cut down, the oak spirit vanishes. If crime increases in a city and the idea of 'justice' is replaced by 'vengeance', a good number of Justice spirits would die. If a spirit puts all of his effort into it, the most he can do to the material world is nudge something or whisper a handful of words. They are all, sadly, subject to the whims of us ignorant humans.
That is, unless they can make a deal with a Medium and absorb some Wisp.
What kinds of Spirits are there?
The secret societies of the material world have wrote massive complex tomes on the number and classifications of spirits that they deal with, but most can be divided into six groups.
Nature spirits, sometimes called Greenlings, are the oldest and arguably the most powerful entities on the astral plane. They are also the most difficult to cut a deal with. Typical domains of these creatures include natural events, (storms, volcanoes, seasons), elements (earth, fire, wind water), and plants and animals (trees, birds, plants, cats, wolves).
Greenlings have an inhuman mindset, and a almost snooty sense of pride. Most dislike humans, and are the most likely to simply try to take Wisp from Mediums without bothering to make a deal. They do not understand humans, and don't bother trying to. At least their desires are very simple; more trees, more storms, more fire, more room to grow, more rain, more soil, more dog treats, more more more. The only beings of this class that seem friendly are the spirits of domesticated animals.
Nature spirits are terrifyingly powerful, and are rarely subtle. Mediums usually deal with Greenlings if they want an bodyguard, something destroyed, or just a huge display of power. Mediums in the past have ruined small towns that have angered them with the might of a single Fire Elemental or Storm Greenling.
Tech Spirits, or Sprites, are typically the first spirit a Medium encounters. They are the spirits of all things that Man has created, even if they were made unintentionally (like pollution spirits). Sprites are also the easiest to deal with. They were made to serve, and desperately, desperately want to be useful to someone. Sprites cling to their Mediums, begging for recognition. They are deeply loyal if the object they embody is properly taken care of. They are just as inhuman as Nature spirits are, though. Sprites don't care if they're serving a mass murderer or a devout priest, they just want to be used.
Sprites are thought to be the weakest of all spirits, and that is true in terms of raw power. The only other thing that tech spirits can do with Wisp other than manifest is improve her object. A laptop Sprite can become as fast as a super-computer. The gun of a Gun Spirit can always hit it's mark with normal bullets the pierce armor. A Shirt Spirit can defend his master from the most devastating attacks to the torso. Most Mediums use the Sprites of a vital piece of equipment to stay safe or to make money.
Virtue Spirits, or Muses, embody the intellectual aspects of humanity. Art, Music, Science, Sports, Righteousness, Paranoia, Tyranny, Treachery, Perversion and Plans are examples of Muses. Though they are given noble names, Muses do not necessary have to be beneficial to humankind, they just have to be a concept above base urges. Muses typically are easy to deal with and understand, though unlike Sprites they do not have a universal love for Humans. Muses also do not always get along with other Muses, though all other classifications will band together in a time of need. Virtue spirits are prone to squabbling amongst themselves, their Mediums, and making drama in general.
Muses are subtle, but powerful. When empowered with Wisp, they can control and alter the thinking patterns of humans to a limited degree, or bestow great skill on humans or other spirits. When Mediums need to sway the masses or inspiration to get the job done, they call for a Muse.
Vice Spirits, also known as Demons, represent the base emotions and states of being of both humans and animals. Examples include lust, fear, anger, hate, need, pain, sickness, weakness, love, warmth, shelter, rape, addiction and hunger. Though Vice spirits do represent some good qualities, they pick up their 'demon' title from their drive to influence as many people as possible with their domain. They are surprisingly friendly, but it is difficult to tell if Demons are grateful for a chance to affect the material plane or if they're trying to manipulate you.
Vices are similar to Virtues with their strong control over the human mind, but they're the only class of spirits willing to damage their domain (a hunger spirit banishing hunger, for instance) so long as they are compensated. Demons seem to have limited precognition, and do make good advisers, if you can trust them. They are tricky spirits though, and given the chance they will spread their domains across the land like wildfire.
Ghosts are the souls of mortal creatures that cling to existence. Most Ghosts hang around due to some horrible trauma in their lives (particularly what caused their death) or to complete some unfinished business on earth. They are the easiest of spirits to understand, but not necessarily the easiest to deal with. Ghosts often seek out Mediums when they hear of them for help completing their works on earth. Curiously enough, Ghosts exist on their own dank little plane, separate from all other kinds of spirits. They can get access to the Astral plane with some wisp.
Ghosts empowered with Wisp can manifest as a healthy, living human being. Their manifested form is far more powerful than that of other spirits. Their strength, agility and endurance is enhanced far above human levels. Ghosts also posses great necromantic abilities, and are good at evoking fear.
Manifestation: The first thing a spirit uses his wisp for is to manifest. Their bodies turn from energy into matter, granting them a form to interact with the world directly. Most Mediums don't understand the immense sense of liberation that comes with manifesting, and why spirits prefer to spend all their time as solid beings. They are slightly more vulnerable, however. If a manifested spirit's body is destroyed, all of their wisp is lost and they need to be recharged before reforming it.
A spirit's body can appear as anything it wants, but is influenced by the expectations of a Medium. They are generally humanoid, attractive, but are clearly not human (excluding ghosts).
The Fold: The Fold is a catch-all term for all the Medium organisations. Most are religion-based, very old, and all know how to train Mediums. They look down on born Mediums, but have no problems training them, if the prospective Medium meets all of their requirements.
The Fold generally keep to themselves. Some, however, are locked in bitter secret wars, and practice 'aggressive' recruitment tactics. Born Mediums are a prime target for abduction, and are forcefully pressed into their organisations.
Hunters: For ages Mediums and Spirits traded, fought, lived, and died together on their planes, hidden by ritual and superstition. Both groups believed that they knew all that existed.
They were wrong. There are Others.
Coinciding with the appearance of born Mediums, a strange violent species began to haunt both Astral and Material planes. They struck out against Mediums and Spirits, hunting them down in their homes. They were more alien than nature spirits, and never held the same appearance twice. All sorts of force was used against the creatures, but they only had two weaknesses. In the Material plane, an materialized spirit could banish the Hunter. In the Astral plane, only the Wisp of a trained Medium could turn it aside.
The Fold are investigating, but are having trouble dealing with the world outside their monasteries and churches. The Born Mediums seem to be hunted by the creatures the most. Perhaps there is a connection...