How’s this for a suggestion?
Penitent’s Knout - Acts as a whip but can be 'A’ctivated to self-flagellate, bestowing a ‘mystical fervor’ of some sort.
or perhaps:
Slumbering Spear - A heavy leaden spear that deals blunt damage, but may be briefly ‘awoken’ to preform a single powerful strike.
If it were possible I’d suggest a weapon that only functions at day/night
Unrelated note, have you thought of added a morale bonus to some of this mods items for those that have the spiritual perk?