Demonic Possession¶
"Once a demon's soul has a strong enough hold there is no way to separate it from the body without killing the body too." — from the Terrun Compendium (S384)
A demon without a body is a spirit decaying toward the Abyss. To stay on the Material Plane it must take a body, and it takes one by possession: a contest of essence against spirit in which the demon, if it wins, "can choose to possess the target (leaving their own host or splitting their essence if they are able to)" (S333). This page covers who can be possessed, what possession does to the host, how demons change bodies, the thralls and familiars that are its lesser forms, and how the possessed are freed or imprisoned. The bodies themselves are on Demonic Forms.
Taking a host¶
Possession is "when multiple spirits fight for control over a single form. This is normally an unnatural and forced event" (S018). In the Fourth Age account the contest is one of essence: the demon and the mortal spirit grapple at the end of each bout of struggle, and the demon loses a tenth of its essence to corruption if it fails (S333). Sometimes the host is willing (S019). When a demon first enters a body "the host remains exactly as they were before being possessed," and it takes a metamorphosis cycle before the demon can begin remaking it (S333). After ten days the host is gone past recovery: a body a demon abandons "will die in 2d6 Bouts if the demon has been inhabiting it for longer than 10 days (the host's spirit is beyond repair at that point). If the demon has not been inhabiting it that long, the host will regain consciousness in a few hours," though "it may take months for them to fully recover their vitality and health" (S333).
A body held for ten days or more is also closed to other demons: "forms which have been stripped of their former spirit are now attuned to the possessing demon and other demons are unable to occupy it," and demons "fortify their forms against possession and the form is destroyed before allowing another demon to occupy it" (S333). A demon may also abandon its body and go hunting as a bare spirit, "generally … only done as a last resort when the demon's host form has been captured or incapacitated," or to hand a captured form up to a master (S333). Demons who possess as a bare spirit fight "at 50% essence strength" (S329).
Host capacity and transformation¶
Every body has a capacity for essence, and "exceeding capacity causes exposure and Essence Decay" (S334). A demon raises that capacity in its metamorphosis cycles, at the price of visible corruption in the host, red or glowing eyes, black nails and teeth, a spined back, horns, acid blood (S333); the stages are given on Demonic Lifecycle. The Sancturi-era account describes the same thing from the outside: "once a demon has infected a body, their natural form begins to take over and the form which they are inhabiting will transmorph into their true form. How quickly this happens depends on what kind of demon and how much control they have over their ethereal energy, the spiritual power of the host, and whether the demon desires to retain their host's form for a while" (S519). In the oldest account the transformation was inexorable: "a demon may be born into any body, but their natural form will quickly take over" (S384).
Who can be possessed¶
Not everyone. "Due partly to the magic of the abscission, and partly to the strength of a being's spirit, a Demon is not able to possess just anyone. Demons possess weaker spirits such as lower animal life forms or those that have depleted much of their available spiritual energy (ethereal), such as spellcasters. Even then, an area where the Abscission has been weakened is usually required. However, the host also needs to be a match for the demon. More powerful demons are not able to possess creatures that would be unable to transform into their natural form. It is this reason that Archdemons have not been able to easily escape the Abyss" (S519). The Fourth Age rules put it as a matter of stratum: a Demon Prince of Bhaal could only be summoned into a living form fit to hold him, which is why his cultists hunted a captured fae (S341).
Weakened spirits are the first to go. Spellcasters, who spend their spirit, are "especially vulnerable to possession when they use their magic" in blighted places (S519), and "a person may become possessed by a demon due to the weakening or wounding of a person's spirit. This is especially prevalent with magic-users" (S384). The hollowed are next: inside a Hollow a person "loses mental and spiritual stats as the hollowing progresses. This makes them very vulnerable to possession by a devil/demon. This possessed hollowed form is able to leave the hollow, unlike the Hollowlord and its minions whose forms are restricted to the Hollow that supports them" (S146). And the unborn: "after the Shattering, Demonic Souls are able to penetrate and cohabit the bodies of weakened spirits and those of the unborn of Terrun. A few years after infection, the demon's soul will be able to take full possession and transformation into a demon will occur rapidly after. Killing the body only starts the cycle over again" (S384).
Where the Abscission is thin¶
The barrier that keeps demons from the world is the Abscission, and possession follows its weaknesses. "The abscission can be locally weakened through repeated spellcasting or the repeated release of ethereal energy (death) in an area. Areas with a weakened Abyssal barrier that are known for demonic possession are often referred to as Accursed. In some cases the Abscission becomes so weak that the boundaries between Abyss and Material Plane have blurred, creating a region known as Demonblight. The demonic energy radiating from the Abyss into these areas kills or corrupts everything in the land around it. Animals that wander into these areas are immediately possessed by hordes of demons waiting for a chance to escape the Abyss" (S519). A Demonic Rift "is a complete break in the Abscission wall … not a natural or accidental event" (S519); the spawning rifts of the Fourth Age "are very difficult to close and most scholars believe that closing one simply forces another to open somewhere else" (S333). The Demonblight of the bone demonlord Vileryth in the Rift is such a region (S050). "There is a very strong correlation between the scale of magic-use in an area and the occurrence of Demonic births" (S384), and the common fear of magic grows from it: "the majority of the masses see magic as just another part of the abomination of Demons" (S519).
Voluntary possession¶
"Some beings voluntarily become possessed by a Demon. There are several known rituals to accomplish this. The primary reason to allow demonic possession is tap the spellcasting power of the demon. This is the only known method a non-spellcasting mortal can gain true spellcasting ability. This leaves the demon and spellcaster in a constant battle for possession of their body. Casting spells in this case is actually a relief for the mortal host as it diminishes the power of the demon inside them" (S519). Spellcasters who summon a demon "usually provide a host" for it as part of a pact or contract (S333); see Demonic Magic.
The other reason is imprisonment. The greatest demons "who were they to take on their true form would be unstoppable" are held in the bodies of volunteers: "this is the case for the Archdemons who have escaped the Abyss since the Abscission. They can no longer be forced back to the Abyss and must be contained using hosts that volunteer to keep them controlled for several years at a time" (S519). "The host will need a lot of outside assistance to maintain control and will be capable of containing the Demon for only a short period … Other demons which were unable to be banished were simply buried deep underground, where their immortality works against them" (S384). The Archdemons page records who holds whom.
Thralls and familiars¶
Not every possession is total. A demon that corrupts a mortal soul without displacing it makes a thrall, a demonspawn "corrupted and turned into a thrall under the control of a Demonic Spirit" (S334); demons also keep bodies in reserve. The Hollowlord Hez'Vandros kept "8 Hollowed Thralls - (7 humans, 1 dwarf) … as extra bodies should any of he or his devils need them. Generally he keeps them out of sight except for 1 or 2 he uses as waiters" (S145). In the Icy Hollow of Hal'Gamesh a Hollowlock necromancer laboured on a Patchwork Abomination, "trying to make a living vessel large enough for a greater demon" (S138), while the Hollowlord's lieutenant "saves the forms that are good for possession" (S138). The tailor Zaena Greyson "has been tortured and possessed by the demon Xokoth," who wore her as a spy (S151); the Boreal Elf shaman of a Scourged band was "possessed by an Eye of Teneb'Vari" (S056); and a demon-fuelled rat-god took the body of the Marshford adventurer Kjell (S359). Valtor's apprentice could "spirit walk to possess different player characters," swapping to another once one was subdued (S040).
A witch's familiar is a possession in miniature: the Malefica rite is to "take a trapped animal and replace its spirit with a demon," after which the witch can see and hear through its eyes and channel curses through it (S228); see Witchcraft.
Exorcism, wards and entrapment¶
"Most Priesthoods also include rituals to detect and exorcise and banish Demonic Spirits, as well as to gauge Abscission levels" (S519). Timing is everything: "normally, these people are identified, and then the demon's soul is exorcised and banished to the Abyss. Many parents prefer to have a priest present at birth to perform rituals that will detect demonic possession. Early detection is critical for exorcism to be successful without killing the host" (S384). "Sometimes, an exorcism can be performed before the possessor has taken full control (and mutated their target form). When successful, the exorcism is treated like a natural form death for the possessor" (S421). The alchemists of Valyr brew a demonsbane draught that "can help protect the drinker against demonic possession and corruption. It is also forced down the throat of possessed people to aid in exorcisms" (S335), and the White Fire's wards "repel demons from an area" for "even hundreds of years" (S335); see Demonsbane and the Order of Valyr. In the Hollows the taint runs the other way, and the hollowed show "vacant or glowing eyes and may be entirely insane and driven by the needs of the Hollowlord" (S325).
The Fifth Age bestiary describes form entrapment, the demon hunters' art of killing a demon's body without its thread so that it remanifests "where the demon hunters have prepared a living prison (usually a crippled humanoid form which has already had the soul removed)," a craft the Druids of Nyx make frequent use of (S019).
Earlier accounts¶
The cosmology of the Earlier Ages explains possession as projection: a demon's spirit crosses as a projection, "a battle between spirits ensues and if the projection is the victor than the projection's natural form disintegrates and their spirit takes over full-time control of the new form. The old spirit remains trapped in the form it no longer controls until that form's death. In moments of weakness, the old spirit may be able to re-assert itself. When the possessed form dies, both spirits act as if their natural form has died" (S421). "Possession of an Immortal does not appear to be possible" (S421). A later revision notes that before the Mithis Plane was destroyed "demons commonly projected their spirits out of the abyss when summoned to take possession of material forms. This still happens, but to a lesser degree. Now they are able to be summoned with their fully manifested demonic forms. When a demon's form dies, it can also choose possession over an immediate return to a newly reforming body" (S018). The compendium adds a third mode, "for a Demon's spirit to be injected into a person alongside their normal spirit," ending in one consuming the other, "most often the demon spirit wins out unless there is substantial outside help" (S384). The Sancturi-era demonologies hold that only Hellspawn "can resist changing their host's form unless they want to, whereas other demon forms cannot control the transformation of their host," and that a Vile "cannot help bursting forth into their natural form almost instantly" (S518); see Demonic Lifecycle. The same text as S519 appears unchanged in an older copy (S513).
In Play¶
The possessed are found by what they lack: the thrall who no longer learns, the spellcaster who casts to feel relief, the child born where too much magic was spent. In the Hollows and the Demonblights there is no safe body, and a party's beasts are the first to be taken (S519). A demon that has worn a body for more than ten days cannot be exorcised without killing it; one that has worn it less can be driven out and the host may wake in a few hours (S333). Demons who lose their body do not die, so the hunters' real work is to find and destroy the Mortiquery, or to have a prison ready where the demon will remanifest (S019).