The Undead.

You have entered into a pact with a shinigami, a fearsome spirit of the netherworld, with powers of death and possession. Shinigami themselves are beings of variable character, some playing active roles in the lives of their emissaries, others inscrutable and shrouded in mystery. All, however, serve a singular, ultimate purpose: to perpetuate death. Those who wield a shinigami’s power spin magic of shadow and authority, puppeteering objects, creatures, servants, and thralls. Such magic is as vicious and precise as it is hated and feared; even those with noble intent who enter into a shinigami’s pact become equal in terror to the evil they seek to vanquish.

Level 1 Features:

Shinigami Magic.

When you learn a spell of the appropriate level using your pact magic feature, you also learn the spells on the Shinigami Spells table. The spells count warlock spells for you, and do not count against your spells known.

Grave Touched.

Your patron's powers have a profound effect on your body and magic. When you hit a creature with an attack and roll damage against the creature, you can replace the damage type with necrotic damage. In addition, once per turn when you deal necrotic damage, you can roll one additional damage die when determining the necrotic damage the target takes. You may add this additional damage a number of times equal to your proficiency modifier, and you regain all uses of this ability upon completion of a short or long rest. Additionally, you have advantage on any saves against a spell, ability, or attack which causes the frightened condition.

Level 6 Feature:

Form of Dread.

You manifest an aspect of your patron's dreadful power. As a bonus action, you transform for 1 minute. You gain the following benefits while transformed:
-You gain temporary hit points equal to 1d10 + your warlock level.
-Once during each of your turns, when you hit a creature with an attack, you can force it to make a Wisdom saving throw, and if the saving throw fails, the target is frightened of you until the end of your next turn.
-You are immune to the frightened condition.
You can transform a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.
The appearance of your Form of Dread reflects some aspect of your patron.

Level 10 Feature:

Mortal Husk.

Your connection to undeath and necrotic energy now saturates your body. You have resistance to necrotic damage. If you are transformed using your Form of Dread, you instead become immune to necrotic damage.
In addition, when you are reduced to 0 hit points, you can cause your body to explode. Each creature within 30 feet of you takes necrotic damage equal to 2d10 + your warlock level. You then revive with 1 hit point in your previous space, along with your carried items and equipment, and you gain 1 level of exhaustion. Once you revive this way, you can't do so again until you finish 1d4-1 long rests (a '0' meaning the ability is immediately available again).

Level 14 Feature:

Spirit Projection.

Your body is now simply a vessel for your spirit. As an action, you can project your spirit from your body. The body you leave behind is unconscious and in a state of suspended animation. To all observation it appears dead.
Your spirit appears in a space adjacent to your body, as a hazy, translucent copy of your living form and can remain outside your body for up to 1 hour or until your concentration is broken (as if concentrating on a spell). When your projection ends, your spirit returns to your body or your body magically teleports to your spirit's corresponding location on the material plane (your choice).
While projecting your spirit, you gain the following benefits:
-Your spirit and body gain resistance to bludgeoning, piercing, and slashing damage.
-Your spirit form gains advantage in saves against effects causing the following conditions: Charmed, Exhaustion, Frightened, Grappled, Paralyzed, Petrified, Poisoned, Restrained.
-When you cast a spell of the conjuration or necromancy school, the spell doesn't require verbal, somatic, or material components that lack a gold cost.
-You have a flying speed equal to your walking speed and can hover. You can move through creatures and objects as if they were difficult terrain, but you take 1d10 force damage if you end your turn inside a creature or an object.
-While you are using your Form of Dread, once during each of your turns when you deal necrotic damage to a creature, you regain hit points equal to half the amount of necrotic damage dealt.
Once you use this feature, you can't do so again until you finish a long rest.