Half Damned: A person born with less than a full allotment of Anima, the stuff from which the soul is made. They are called this because of their tendency to draw the attention of corrupt spirits and become dangerous and powerful.
Rider: When a spirit places itself within the body of a half damned it is known as a rider.
Spirit: Immaterial creatures with a great deal of power, but very little ability to use it. Should they manifest through a half damned they can exert a vast array of power in the physical world.
Occupation: When it is said a half damned is occupied it means that a spirit(or spirits, theoretically) is riding the half damned.
The Nature of Spiritual Entities
Spiritual entities are elemental in nature. Fire, Water, Air, Earth, and Aether each have their own court of spiritual entities. As you the spirit takes more control, the body of the half damned host begins to align itself more with the elemental nature of the spiritual rider. This has led to the rise of magical races of man: Undines(water), Jinn(fire), Cthon(earth), Harpies(wind), and Daemons(aether).
Undines: When a pure spirit they are spirits of emotion and artistic muse. When they manifest through a half damned they become secretive creatures of obsession and desire.
Jinn: When a mere spirit they are innovation and willpower. When inhabiting a mortal form they become singularly focused on social systems and analyses to the point of paranoia.
Cthon: In the spirit they are growth and endurance. When they occupy a person they become secretive and stubborn. They view no life as valuable, save for their own.
Harpies: When in the spirit they are protectors and healers. Occupying a mortal frame they become greedy and gluttonous beyond all reason. They are called the snatchers, for they will take from you until it hurts.
Daemons: Spirits of intellect and reason, when they inhabit a mortal frame they become tainted with desire and emotion. They will twist the truth into lies and break oaths almost as a rule.
Your character is created as normal for Fate Core with one exception. Replace the last aspect of the Phase Trio with your Rider aspect. Your Rider aspect represents the core desire of your spirit rider. This aspect is created by the person on your left and acts as a second trouble aspect.
You have a corruption consequence track of three consequences, whenever you need it you can tap into it and gain a corruption consequence and also a power bonus. The first time you gain a bonus point of refresh, the second you gain two refresh, and the third you gain three. Each consequence requires two fate points to refuse the compel(rather than the normal one). Your corruption fate points need to look different from your normal fate points, or have some other way of keeping track of them.
There are three consequences you can take when taking corruption: Delirium, Stigma, and Blight.
Delirium: This represents a mental consequence. It is giving in to the desires of your Rider and manifesting emotional and intellectual traits that are not your own.
Stigma: By channeling the energies of the spirit world your physical form begins to alter in obvious and disturbing ways, whether it be through skin tone, restructuring of the body into a more alien form, or even stranger. When you are exhibiting Stigma, you cannot pretend to be normal.
Blight: When you are manifesting Blight the world around you cannot abide your presence. Whether it is through waves of heat, ice, moisture, desiccation, strong emotion, or whatever else this consequence is the most disturbing. It makes it impossible to hide, and fills the world with more pain. Only other half damned can avoid the damage of your Blight.
Recovering from corruption consequences requires a lot of work. All of them are treated as severe consequences for the purposes of recovery. Once the requisite time has gone bye you must take specific action related to your desire to rid yourself of your rider. When you recover you lose the bonuses along with the consequence.
Once you have a consequence you can gain corrupted stunts. Corrupted stunts only work when you have an appropriate corruption consequence. When you have a corruption stunt you can invoke your corruption aspect to instantly succeed with style at a task, no roll required. You can even use it to succeed with skills that would normally require special knowledge or equipment. It will let you shoot someone even if you don't have a gun, or perform surgery drunk with no skills.
Let me know what you think.