The Undying Soul

Whether it be a personal experience or someone in you past, at some point your bloodline has been faced with death, and on the return back to life a corrupting essence fused into the bloodline and left a undying magically taint. 

You gain an unnatural ability to manipulate death, and that which defies it. You have an innate assess to a variety of necromancy spells, and can manipulate your own life force.

Expanded Spell list

1st- Inflict Wounds, Cause Fear

3rd- Ray of Enfeeblement, Gentle Repose

5th- Animate Dead, Vampire Touch

7th- Shadow of Moil, Blight

9th- Negative Energy Flood, Danse Macabre

Aura of Corruption

As a bonus action you can unleash your Aura of Corruption which magically wreaths you in black necrotic magic, yours eyes turn pitch black and the shadows curl around you. For 1 minute, you gain the following benefits:

• You absorb all light within a 10-foot radius, giving disadvantage to any ranged attacks made against you.
• Any creature that is not classified as undead takes necrotic damage equal to your charisma modifier every time it hits you with a melee attack from within 5-ft of you.
• Whenever you roll necrotic damage on your turn, the roll gains a bonus equal to your charisma modifier.
• You have resistance to necrotic damage

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

Relentless Spirit

If you are reduced to 0 hit points, an undead spirit busts out of your chest and continues to fight for you. While this spirit is out you must still make death saves, but you can continue to fight through your spirit on your turn. The spirit remains for 1 minute or until killed, and once gone, it cannot be summon again until you finish a long rest. 

(Stats- https://www.dndbeyond.com/monsters/1290236-relentless-spirit)

Life Stealing

Starting 14th level you gain the ability to draw life force from your necromancy. Whenever you expend a spell slot to cast a spell that deals necrotic damage, you regain hit points equal to the spell slots level + your charisma modifier. 

Unnatural resistance

At 6th level your body has grow stronger and now have resistance to necrotic damage. Also when your aura of corrupt is active you now gain immunity to necrotic damage rather than resistance.

Undying Protector

At 18th level, you have mastered death and your aura of corruption is even stronger.

You now have advantage on death saving throws, and as a reaction you can grant this advantage to anyone within 30-ft of you.

While your Aura of Corruption is up you gain these additional benefits:

• You gain resistance to all damage
• If anything dies within 30-ft of you, as a reaction you can raise it as a ghoul under your control. You can only have 2 ghouls at a time.
• When hit with necrotic damage, you instead heal for half the damage done