Possess permanently removes the user from the active party and causes Death to a single target overriding the target's Death protection, and thus it works on all enemies, including bosses, since there are no resistance checks for Possess. However, as the Ghost only joins on the Phantom Train, this cannot be utilized to its fullest extent.
If the Possess command is hacked into one of the thirteen playable characters' command lists, except for Umaro, the character that used the Possess command and successfully killed an enemy will be removed from the player's current party and will be loitering on board the airship. The character will be available to be put back into the player's party when the player visits the airship to switch characters.
If a ghost is hacked or glitched into the party, Gogo will be able to equip the Possess command.
Spirit possession is a paranormal or supernatural event in which it is said that animas, demons, extra-terrestrials, gods, spirits, or other disincarnate entities take control of a human body, resulting in noticeable changes in health and/or behavior.