Draug

Your spirit is one tarnished by death. You are akin to a living corpse, fighting on the battlefield without a care for your wounds and survival. Those who may take you down have to kill you twice, or else they may find themselves in a grave before you. With time, your restless spirit may even gain the ability to possess other lifeless bodies so you may continue living.

Reaper's Blade

Also at 3rd level, you can channel your connection to death through your weapon. As a bonus action, you can imbue your attacks with two benefits of your choice:

When dealing damage to a creature through a weapon attack, you can choose to deal necrotic damage.
Once per turn, you can cause a creature you hit to be poisoned until the start of your next turn, or take extra damage equal to half your level in this class. This creature must not be undead.
Once per turn, you can cause an undead creature you hit to take an additional amount of damage equal to one of your weapon's damage die.
Creatures don't provide cover to creatures you attack.
Creatures hit by this weapon can't regain hit points until the end of their next turn.

This lasts for 1 minute, until you die, or you end it early (no action required).

You can choose more benefits as you progress in this class, increasing at 7th (3), 10th (4), and 15th (5) level.

You can use this feature a number of times equal to your proficiency bonus, and regain all expended uses after a long rest.

Touched With Death

When you take this archetype at 3rd level, your body has been close to death so many times lesser dangers don't faze you. You are immune to diseases, have advantage on saving throws against being poisoned, and you have resistance to poison damage.

Return from the Grave

At 7th level, the doors to the afterlife are often closed to you. You no longer need to eat or breathe.

If you start your turn at 0 hit points, you can use your Second Wind feature as part of starting your turn, bringing you back from 0 hit points. Doing so brings you standing without costing any movement, and until the end of your turn, you have advantage on the next attack roll you make against the creature that brought you to 0 hit points.

Possess Corpse

At 10th level, you can transfer your spirit into another body. As an action, choose a corpse that you can see within 60 feet of you. For the next number of minutes equal to your proficiency bonus, you possess the body, controlling it, and your actual body drops prone into a catatonic state. Your game statistics are replaced by the statistics of the corpse, though you retain your alignment, personality, fighter class features, and your Intelligence, Wisdom, and Charisma scores. If the target has any class levels, you can’t use any of its class features.

While in this body, you gain an amount of temporary hit points equal to 5 times your level in this class. Your actual body does not possess these temporary hit points.

This feature ends once your temporary hit points drop to 0, your original body drops to 0 hit points, or when you choose to return to your body as a bonus action.

Once you have used this feature, you can't use it again until you finish a long rest.

Restless Spirit

At 15th level, your spirit is resilient to grueling work.

You no longer need to sleep, and gain proficiency in death saving throws.
You can't gain exhaustion by any means other than spending 24 hours without a long rest.
Your Reaper's Weapon ignores immunities to the Poisoned condition, and treats immunities to necrotic damage as resistances.

New Body

At 18th level, you can occupy a corpse, permanently. You can target undead creatures, with a challenge rating equal or lower than your level in this class, with your Possess Corpse feature. When doing so, you make a Constitution check against their Charisma saving throw. If you succeed, you take over their body. For the duration, your target can perceive from their body using its own senses, but it can’t move, talk, or take actions at all.

Additionally, you can possess a corpse through your Possess Corpse feature for up to one hour. If you remain in this new body for the full duration, the possession is permanent, causing your previous body to die and your new body to regain hit points equal to the amount your previous body just had.