Certain creatures can attempt to possess characters, taking over the character‚s body entirely. First, when a creature attempts to possess someone, he must make a Possession check against the defending character‚s Will. The creature‚s entry will detail what the creature‚s bonus to this check is, as well as other details (such as maximum range of the possession ability).
If the possession check beats the character‚s Minimum Will, he takes a morale penalty (untyped damage).
If the possession check beats the character‚s Will, the character is possessed. Now the defender and possessor have equal control over the character‚s actions. On their respective turns, they can direct the character‚s body to act. However, the body can‚t act for more than six seconds per turn, which could be three seconds each from the possessing creature and the possessed character, six seconds from one and none from another, or any combination thereof. Whoever is currently controlling the character uses their own skill bonuses and techniques, their own mental ability scores (intelligence and spirit) but the possessed character‚s strength, endurance, and dexterity. Acting characters can use only their own combos and cast only spells that they know.
Either of the actors involved can attempt to veto the other‚s turn. To do so, make an opposed Will Check (1d6+Will). If the acting character wins, he has control for the turn and the vetoing character takes a morale penalty. If the vetoing character wins, the acting character‚s turn is skipped. In cases of a tie, roll again. A character with zero Will cannot attempt to veto.
In this example, the fell demon Bal-Ziggaroth attempts to posses the hero Jack Clancy. First Bal-Ziggaroth makes a Possess check (his bonus is +4) against Jack‚s Will (9/3). Bal-Ziggaroth rolls a 6, meaning his total Posses check result is 10, so he succeeds. Jack is now possessed.
Bal-Ziggaroth acts before Jack in the initiative count, and decides to use Jack‚s body to shoot one of his comrades. Jack, wanting none of this, decides to veto Bal-Ziggaroth‚s turn (risking a morale penalty in the process). Each makes a Will check (1d6+Will). Jack‚s Will is only 8, while Bal-Ziggaroth‚s Will is 11. In the end, Jack only got 12, while Bal-Ziggaroth got 14. Jack fails his veto, takes a morale penalty (dropping his Will to 7/2), Bal-Ziggaroth is able to control Jack‚s body for his turn. Bal-Ziggaroth shoots Jack‚s friend using one of the demon‚s own combos (taking four seconds) and takes no actions for the remaining two. On Jack‚s turn, he has two seconds to use (which Bal-Ziggaroth can attempt to veto).
In an unlikely but theoretically possible scenario, a creature can attempt to possess a character and work with him, instead of against him. In this case, the character can deliberately allow the creature in (negating the need for a Possession check). Then, when either one acts, they can use the highest skill modifiers and mental ability scores of both the possessor and possessed, as well as techniques, and spells and combos known from both. At any point, either can stop working together and begin vetoing the other‚s actions, just as a hostile possession attempt can turn cooperative if the two characters involved decide to work together.
Multiple creatures can attempt to control the same character‚s mind, each vying for dominance. If attempting to possess someone who already is possessed by one or more creatures, the initial possession check is made against the creature with the highest Will. However, that creature can deliberately forgo the check (and take no risk of a morale penalty for failure), meaning the check is made against the second-highest Will. That creature can similarly refuse the check, and so on. If the possession check is successful, that creature can now attempt to control the character‚s body as normal ƒ but has to struggle with more parties. Any of the creatures involved can attempt to veto any of the others‚ actions. A single creature can attempt to veto any number of other creatures (risking morale penalties each time), but no more than once per round against any one creature. The body, as always, can take no more than six total seconds of action per round.
If a possessed character gains the Broken condition (has Will of zero), he can no longer attempt to veto other creatures, nor act on his turn. He is still alert and can use all of the body‚s senses, but can‚t actually act in any way. The character cannot remove any morale penalties without outside help (such as an ally inspiring him with Charisma). If a possessing creature gains the Broken condition, it ends up in the same situation. A Broken character cannot aid another possessing creature with a cooperative possession (see above). A Broken creature cannot attempt to flee (see Ending a Possession, below) without permission of all other possessing creatures.
Generally speaking, creatures can choose to stop possessing a character at any point on their turn as a 0SA. However, this action can be vetoed by another possessing creature or the possessed character, thus trapping the creature. A creature whose escape attempt has been vetoed takes a morale penalty.
Possessions can also be ended forcibly, such as with an Exorcism (see the Faith skill).