Diabolic Lineage

Its quite rare, but some tieflings are born with the innate ability to shape change. However this is quite difficult to perform. For those who practice this skill can tap into their fiendish nature and become a different type of fiend. They turn into a large fiend and gain +6 strength and constitution ignore 20 limit.Their bone propagate into living knuckle weapons. They gain the fire-bolt cantrip magic user or not. This transformation lasts until the fight is over or cut off early and afterwords they have to roll a Con save of 15 to succeed or they gain fatigue. You still retain all damage received as the higher demon so if you get hurt for more than you have in your original turn you will go down to one health.