[Snake]

My take on this:

Soul Guide - If you defeat an enemy who is a Ghost, Possessed or Undead, you will reap some of their essence and restore HP/FP equal to Character LV * X (2 + 1 per 1 Spirit).

If the opponent was possessed by spirits, they will also be afflicted with Spirit Shock, which disables their Spirituality Talents for the duration of X rounds (25 or so?). This lasts between multiple battles.

The (cooked) IC: A bond between a Possessed and their Spirits is something the Reaper/Appertaurus can naturally disturb with their racial magic, therefore weakening the link between a spirit and the ones they are possessing. This is a key process to successfully exorcising through force, yet and however, the rest of the procedure requires the victim's own mental push to be completed, and the opposite may as well as happen, in which through sheer willpower they can retain those bonds and strengthen it once more over time.