Possession

Possession is the magical effect of one creature inhabiting and controlling the body of another. The canonical example is the magic jar spell; ghosts, certain fiends, and rare class features can also produce possession effects.

General mechanics:

• The possessor's mind takes control of the target's body. The original soul is suppressed (not destroyed) for the duration.
• The possessor uses the target's physical stats (Strength, Dexterity, Constitution, AC, HP, speed) and its own mental stats (Intelligence, Wisdom, Charisma) and class features, skill proficiencies, and known languages.
• The possessor does not gain access to the target's class features, spells, or proficiencies (with case-by-case exceptions in specific spells).
• Damage to the possessed body affects the body, not the possessor's original form (which is typically stashed elsewhere or absent).

Entering and leaving possession:

• Possession typically requires the target to fail a Charisma saving throw against the effect's DC
• A successful save prevents possession and may make the target immune for 24 hours
• The possessor can end possession voluntarily (returning to its body or container)
• The possessor is forced out when the possessed body is reduced to 0 HP, when the duration ends, or when Dispel Evil and Good / protection from evil and good is cast on the target

Detecting and resisting possession:

• An ally observing the possessed creature can make a Wisdom (Insight) check against the spell save DC to notice that something is wrong
• Detect evil and good, true seeing, and certain divination magic can reveal the possession
• The original soul is restored when possession ends; it remembers nothing of the time it was suppressed