You are dead.
All in all, being dead is not so bad. It’s less “The End,” and more a change in perspective. When you were alive you hated the world and all living things because you were trapped in a horrible little corner of human existence. Now your experience is unlimited. You can go anywhere, see anything. You have a myriad of more interesting reasons for hating the world and all living things. Eventually you’ll resolve whatever unfinished business binds you to this world so you can move on, and see if the afterlife lives up to the hype. For now, though, you’re putting that off so you can have some fun as a ghost.
Possessor Spirits advance as specialists, and share their hit points and saving throws with the Magic User. As ghosts they are completely incorporeal. They can neither be affected by the material world, nor can they affect it. This means they can pass through walls, and are immune to damage from non-magical weapons. However, they couldn’t make a grain of rice wobble if their afterlife depended on it.
When a Possessor Spirit is not attached to a physical body they appear as a monochromatic specter. During character creation the player should select the color of their translucent body: classic white, ghostly green, poltergeist pink; whatever tickles their fancy. They should also figure out what clothes they died in, since that’s what they’ll be wearing for the rest of eternity.
Despite their inability to affect the physical world, ghosts can still speak, as well as experience the world through their senses. They can feel the texture of an object, or taste a bit of food, but they cannot move the object or eat the food. Also, given how most people feel about ghosts, it may prove difficult for the character to socialize with outside their party. Some wizards or monsters might be comfortable having a chat, but most folks are very fleshist.
The best part of being a Possessor Spirit is the possessions. Just gettin’ on into people’s bodies and controlling them like puppets. It’s the best. Characters are able to possess one person, per day, per level. The target of the possession is entitled to a saving throw versus Magic to remain in control of their body. Their save is modified by the difference in hit dice between possessor and possessee. (For each HD the target has above the possessor, they get a +1 to their save. For each HD below, they take a -1 penalty.) If the save is successful, the Possessor Spirit is rebuffed. They take 1d6 damage, and cannot attempt to possess this target again until they level up. A failed possession attempt does not count against the spirit’s limit of possessions per day. If the target’s saving throw fails, the spirit takes control of their body.
While in command of a body, the possessor spirit gains full access to their host’s knowledge and abilities. Any skills, spells, secrets or powers belonging to the host are now at the disposal of the possessor. This open flow of information can be a double edged sword. The suppressed mind of the host gains equal access to the knowledge and secrets of the spirit which supplanted them. They may use what they learn to troublesome effect after the possession ends.
There are a few uncommon limits to a Possessor Spirit’s mastery over their host. Individuals with a heightened awareness of the spiritual world may recognize that a body has been possessed by a foreign spirit, and may even have means by which to cast the spirit out. Likewise, the host’s intimates may pick up on their friend/parent/lover’s peculiar behavior. Any conversation with such a person has a 1-in-6 chance to tip them off that something is wrong. The chance will increase if the possessor is not doing their best to act natural.
If a host dies while a Possessor Spirit is in control, both spirits (the possessor and their victim) are forced out. The victim’s spirit has a 4-in-6 chance of becoming an angry ghost which will return at a later time to seek vengeance for their demise. Otherwise, they pass on to the afterlife. In either case, their burning anger towards the possessor knocks the player character down to 1 hit point.
There is no limit to how long a host can be possessed. However, once a Possessor Spirit leaves a body, that victim will have a +2 to any save made against future possession attempts. This bonus stacks with each successful possession.