At level 3 when you pick this subclass

Disciple of Immortality

As a disciple of Immortality you gain three features. Instead of gaining ki you can meditate to revitalize your body making a short rest take 30 minutes. Your bodily imperfections have been heavily reduced and you will live 50% longer than an average member of your race. Lastly you gain plus 1 to all hit die (con18   Lvl 3     3d8 +15 hp) (con20 lvl 3 3d8 +18 hp)   
 

Con prof

Con prof

Health boost

Health Boost

Power of Immortality

At level six you get more than just longer life as you can start using Your immense Life as a weapon. Your unarmed strikes now can use constitution as their modifier. Instead of gaining ki you can meditate to revitalize your body making a short rest take 30 minutes.
Lastly your unarmed strikes now can do either Radiant damage or Necrotic damage (half damage but lifesteal)

Con modifier punch

Con modifier punch

Radiant or Necrotic

Radiant or Necrotic damage on Unarmed Strike

Aura of Immortality

You can have any hostile entities you choose within a 100ft radius fight only you (wisdom saving throw of 10 + constitution modifier + proficiency) (Targeting Aura) or have any entities run away from you until they are at least 100ft away from you (Wisdom saving throw of 10 + con modifier + proficiency) (Intimidation Aura) the range increases by 100ft at level 13 and 15 and 200ft at level 18

All

All

(Almost) True Immortal

You gain the Tough feat if you don’t already have it, if you do you gain any feat of your choice (that you could already get)  Once per long rest you can survive an attack at 1 hp that would’ve killed you instead, this increases to twice (lvl 18) thrice (lvl 19) and 5 times (lvl 20) (this naturally occurs) you gain resistance to all nonmagical damage aswell as radiant and necrotic damage. Once per long rest you can use all of your Ki        and damage everything in 35ft of you for 1+ con x your Ki. Every 1000 years you gain one maximum Ki. Lastly you cannot die of old age

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All