Undead Warrior

As an Undead Warrior, you have experienced a traumatic or life altering event brings about irrevocable change, pushing you to your new purpose that is spurred on by the power of your sheer will to persevere.  If killed, you are unnaturally revived after 1d4 years. This feature continues into the next life until your purpose is fulfilled.  Upon death, you warrior lose all memories of your past and are returned as Reborn or Undead races. You may come back as another subclass or class altogether, but this feature remains.

Deathless Fortitude

At 3rd level, your Second Wind feature is updated as a result of your deathless nature.   After using Second Wind, you are bolstered for the next minute by your undead nature.  During this time, if you are reduced to 0 HP but not killed outright, you instead regain HP equal to 1 plus your Fighter level.

Persistent Will

At 7th level, you can add 1d6 to a failed saving throw.  This can be used a number of time equal to your Constitution Modifier and resets after a long rest.  This increases to 1d8 at 10th level, 1d10 at 15th level, and 1d12 at 18th level.

Connection With The Dead

At 7th level, your connection and acceptance with death allows you to commune with those who have moved onto their next life.  Once per day you may cast the Speak With Dead or Summon Undead spells without requiring any material components.  Constitution is your spell-casting ability.

Indistinguishable Undeath

At 10th level, your prolonged, deathless existence severs your reliance on your physical body. You are able to shut down your body’s functions and appear dead.  This has all the same effects of the spell Feign Death, including the duration, except you retain consciousness.  You can use this feature once per day.

For one hour, or until you use an action to end the effect, you appear dead to all outward inspection and to spells used to determine the target’s status. You are blinded and incapacitated, and your speed drops to 0. You have resistance to all damage except psychic damage. If you are diseased or poisoned when you start the effect, or becomes diseased or poisoned while under the effect, the disease and poison have no effect until the effect ends.

Constitutional Surge

At 15th level, after gaining the benefits of a long rest, your Constitution score is increases by 4 until your next long rest.  Each time you take damage, you must make a Constitution saving throw equal to 10 or half the damage taken (whichever is higher).  Upon a failed save, your constitution score reverts back to its original value.  This reduction can set your HP to below 0.

Indomitable Fortitude

At 18th level, your Deathless Fortitude is further refined by the ultimate acceptance of your undead nature.  While deathless fortitude is active, if you are reduced to 0 HP but not killed outright, you regain HP equal to 1 plus your Fighter level, and continue to receive this benefit for the next minute.