The way of the iron bone is a non-traditional monk path. Often used by beggars, hooligans and common bandits.

Monks who follow this path rarely meditate, follow spiritual teachings or train in a conventional way. They follow the teaching that in order to make one's self stronger, both physically and spiritually, you must break yourself down and build yourself up again. How can you claim to be pure when you have never felt the full temptation of life, how can you say you are immune to pain if you have never felt you bones break. A master of way of the iron bone is nearly unbroken, physically, spiritually and mentally

Wall of flesh

Your Flesh has become toughed, thick with callouses and scars. 

You can add your Con modifier to your unarmoured defence calculation 10 + Dex + Wis + Con

Wall of Bone

Your Bones have broken and healed and broken and healed becoming stronger and stronger. 

When you roll damage on an attack roll you may choose to re-roll the die and take the higher roll 

Wall Of The Mind

Your mind has become resistant to pain and hardship. 

You become resistant to psychic damage and have advantage on saving throws against being charmed, frightened or stunned. In addition if you were to drop to 0 hp you can expend all remaining ki points to continue to fight, you may take your turn as normal in addition to making death saves. if you take damage you fail a death save as normal and the effect ends.  

Fortress of the self

Your Body has been through hell and back and has come back stronger.

You can expend 4 ki points as an action on your turn to gain resistance to all types of damage and immunity to one damage type of your choice, the state lasts 5 minutes. In addition, while in this state, you can expend a ki point after landing an attack to do the max damage roll possible.