You are looking for the Soul Withering rules, pg 134 in the RMSS rulebook.
1 pt per day of rest, or 1 pt per week if not travelling and generally staying in one place. If in a specially soothing place, rate increases to 2 pts a day or 2 pts a week. If on holy ground, rate increases by an additional 1d10 pts a day or week.
There are also spells to heal drained Co. Cleric base list I believe.
lynn