Restriction: The monk must strive to attain peace and may only use violence as a last resort. He can never strike the first blow in combat. If attacked, he must use the fight defensively action or the total defense action for the first 2 rounds. He must always give his opponent the option to surrender, and cannot purposely slay another creature that could reasonably be influenced to flee or join a civilized society as a productive member (obviously this excludes many monsters). Many monks who have taken this vow learn how to grapple and pin opponents, tying them with specialized knots that allow them to work themselves free after sufficient effort. Many monks of peace are vegetarians.
Benefit: A monk with this vow increases his ki pool by 1 ki point for every 5 monk levels (minimum +1).