Needs review
Source: Way of the Open Hand

Description: The sagasu combines magic with natural skill to inflict greater damage on corrupted opponents.

Prerequisites: Base Attack Bonus +3, Improved Unarmed Strike, Void Use, Sagasu-do Novice, Four Kiho feats or 2nd level divine spells

Required for: Sagasu-do Master

Any time you are affected by any spell that detects, harms, or provides special protection against creatures with the Shadowlands subtype, you gain a damage bonus equal to your Charisma modifier against targets with the Shadowlands subtype on all unarmed attacks. In addition, any time such a spell would normally end (either due to being dispelled or due to the spell's duration ending normally) you may spend a Void Point to make the spell last a number of additional rounds equal to your Wisdom modifier. This may be done once per spell effect and does not affect spells with an instantaneous duration.