Some adepts seek to train their bodies and spirits towards one singular purpose: to defy and overcome death. These masters gain incredible resilience, capable of shrugging off wounds and afflictions that would destroy lessers. It is said the greatest practitioners of this path also slow or even stop their aging, coming very near to the secrets of eternal life.
At 3rd level, whenever you finish a short rest or succeed on a saving throw you gain temporary hit points equal to a roll of your martial arts die + your proficiency bonus.
Also at 3rd level, you may spend exertion points as part of a short rest to roll additional hit dice for healing. You roll one additional hit die per point of exertion spent, and may only spend a number of exertion points in this way equal to half your proficiency bonus.
At 6th level you gain an expertise die on death saving throws. You also gain the ability to resist the pull of death. When you are reduced to 0 hit points but not killed outright you may spent a point of exertion and choose one of the following effects:
You remain conscious and able to act while dying at 0 hit points. While at 0 hit points your unarmed strikes deal additional necrotic damage equal to your martial arts die and if you reduce a creature to 0 hit points you gain a successful death saving throw. You still suffer failed death saving throws from taking damage as normal. If you attain 3 failed death saves you die; if you attain 3 successful death saving throws you regain 1 hit point.
Increase the number of death saving throws you can fail before dying by your proficiency bonus.
At 11th level you are immune to disease, resistant to poison and necrotic damage, and gain an expertise die on saving throws made to resist or end the poisoned condition. in addition, your hit point maximum cannot be reduced.
At 17th level you stop naturally aging, are immune to magical aging, and have no maximum lifespan. You also ignore the first level of fatigue you gain per day, and when critically hit by an attack you may spend 2 exertion points as a reaction to reduce the damage to a normal hit, though other additional effects of the critical hit still apply.