To know how to strengthen one's body, one must first know how it is weakened, and monks of the Broken Back are masters of understanding how to weaken their own bodies in specific, controlled ways to great effect. It is said that the idea of lifting with your legs and not your back came from the founder of the Broken Back in a long and painstaking attempt to help reduce the amount of injuries in his monastery. Above all others, monks of the Broken Back have a mastery of their bodies, allowing them to cause pain in very unusual ways.

 

Ki Blunders

At 3rd level, the following ki features are altered:

• Flurry of Blows: (Sprained Wrist) If you miss a creature with one or more of the unarmed strikes given to you by Flurry of Blows, you may spend 1 additional ki point to maneuver yourself in such a way to sprain your own wrist against them. If you do, you gain 1 level of Exhaustion and your enemies feel really bad about fighting you. The creature(s) you missed with your unarmed strike(s) have disadvantage on their attacks against you until the end of your next turn.
• Patient Defense: (Right in the Kidneys) If a hostile creature deals damage to you while you are Dodging with Patient Defense, you may spend 1 additional ki point to maneuver yourself in such a way so they strike one of your vital weak points. If you do, you gain 1 level of Exhaustion and the creature tries it's best not to harm you again. Until the end of your next turn, that creature cannot make attack rolls against you and any ability from that creature that requires a Dexterity saving throw cannot include you in its range of effect.
• Step of the Wind: (Rolled Ankle) While Dashing or Disengaging with Step of the Wind, you may spend 1 additional ki point to move in such a way that causes you to roll your ankle. If you do, you gain 1 level of Exhaustion and other creatures really want to get out of your way. For the rest of your turn you can move through the space of other creatures, Shoving them as you do so.

Howl of Pain

At 3rd level, whenever you gain a level of Exhaustion you let out a pained howl, causing your enemies to wince and cringe and shudder at the pain that they've caused you. All hostile creatures within 30 feet of you that can see or hear you immediately take a Martial Arts die of Psychic Damage before any effects of Exhaustion take hold.

Additional Key Blunders

At 6th level, the following ki features are altered:

• Quickened Healing: (Cramp) If you roll a 1 on your Martial Arts die for Quickened Healing, you may spend 1 additional ki point to give yourself a cramp. If you do, you gain 1 level of Exhaustion along with a protective layer of forcibly contracted muscles. You roll a Martial Arts die and gain a number of temporary hit points equal to the number you rolled plus your proficiency bonus.
• Focused Aim: (Popped Blood Vessel) After spending ki points with Focused Aim to increase your attack roll, if you still miss the target, you may spend 1 additional ki point to pop a blood vessel from focusing too hard. If you do, you gain 1 level of Exhaustion and your enemy feels an intense urge to avert their gaze. The creature is Blinded until the end of your next turn.
• Stunning Strike: (Fracture) If a creature succeeds on its Constitution saving throw against your Stunning Strike, you may spend 1 additional ki point to intentionally break your bone against the creature in the attempt. If you do, you gain 1 level of Exhaustion and your enemy cringes extra super hard. The creature takes an additional Martial Arts die of Psychic Damage every time you use your Howl of Pain feature until the end of your next turn.

Dead Tired

At 6th level, you no longer instantly die from Exhaustion. If you were to instantly die from a level of Exhaustion, you instead fall Unconscious and begin making Death saving throws at the start of each of your turns. On three failures you die like normal, but on three successes if you have more than 0 hit points you regain consciousness and remove 1 level of Exhaustion. Additionally, you now have the ability to remove 1 level of Exhaustion during a short rest.

Precision Injuries

At 11th level, you now have the ability to trigger Ki Blunders without having to use the original ki feature. If you do, you still gain the 1 level of Exhaustion, but you only spend 1 ki point.

Ignore Pain

At 17th level, whenever you gain a level of Exhaustion you may ignore all effects of Exhaustion until the end of your next turn.