Demonic Possession

Demonic possession is a natural ability similar to the spell magic jar. At will, the demon takes over the host's body and dictates its actions until the demon either leaves voluntarily or is evicted by spells such as "exorcise" or "abjure." This capability is inherent in most demons.

Before a demon can successfully inhabit a being, the potential host has the chance to resist through a saving throw against paralysis. A successful saving throw means the host can fend off the possession.

The concept of demonic possession exists in many cultures worldwide, but the specifics differ. Some belief systems make a distinction between demonic oppression (where an individual is influenced or tormented by a demon but not directly controlled) and possession (where the demon has full control over the individual). Throughout history, there have been numerous documented cases of demonic possession.

Vulnerable Hosts

Naturally, demons prefer hosts with limited wisdom, as a low wisdom score might impose penalties to the saving throw. It's infrequent for demons to target extraodinarily wise or intellectually superior beings. Someone with a limited wisdom or intelligence is less likely to be noticed if they exhibit unusual behaviour, aiding in the demon's possession being successful.

Additionally, a demon might inhabit an ailing or near-death body, which then miraculously recovers. This has led some to assume that any sudden recovery from illness implies demonic possession. This can lead to persecution and occasionally execution, as some cultures believe that burning at the stake frees the possessed soul and drives off the demon.

Detection

The spells penetrate disguise and true seeing can unveil the possession. Still, there are many who believe certain demons can elude this spell, making it appear as though the host is completely normal. Those with knowledge in divination and dweomercraft have means of detecting the presence of demons also.

See also,
Apothecary
Bloodletting (sage ability)
Lich
Mythology