Alastor's Requiem

You channel the soul of the departed to let them still give their wisdom. When you cast this spell, you call the soul of a deceased creature that is free and willing. If you try to summon a soul of a creature that is either alive, not free, or not willing, then the spell fails. You allow the soul of this creature to control your body, while still maintaining your own control. Doing so does put you in some danger. If a soul does something that you don't wish to happen you must make contested Charisma Checks. If you succeed then the spirit may not control your body for 1 minute, unless you allow it, if you fail then the spirit has free control of your body for 1 minute. If you do something the spirit doesn't want to happen (Which includes ending the spell) then you must also make contested Charisma Checks to see who gets to stay in control. If either you or the spirit ever win 3 contested Charisma Checks done by this spell, then the one who won 3 first automatically wins any more contested checks that they are to made to do for the continuation of this spell.

A strong enough spirit could even permanently control your body if you are not careful. At the end of the duration of the spell, if the spirit is in control; it can attempt a Charisma Save against your Spell Save DC +10 to stay. If the soul succeeds then you automatically fail any contested Charisma check to control your body until 24 hours have passed, in which case you may attempt to end the spell with a Contested Charisma Check against the soul. If you fail, nothing happens and you must wait another 24 hours to try again. On a success the spell ends.