Necrotic Bloodline

One of your ancestors was a powerful and feared master of the necromantic arts, or a warlock who made a pact with a Lich. Most try to hide their necromantic heritage, trying to redeem their ancestors for their terrible deeds and actions, but others, in one way or another, try to continue the lineage that their blood carries. Although  it depends on who uses it, many creatures take a dim view of those who use necromantic arts, and much more so of those who have them in their blood.

Necrotic Heritage

An enigmatic necrotic power flows inside you, your spells usually have a certain greenish glow. Your eyes glow the same way when you cast a spell. Additionally,  you can add any spell from the school of necromancy to your sorcerer spell list.

Beyond Life and Death

From 1st level, when your hit points reach 0 and you fall unconscious, your soul detaches from your body and you can move like a ghost. During your turn, after death saving throws, you can use your bonus action to materialize. Once materialized, you can use all your actions, except actions that directly deal damage, after wich, you will become ethereal again. This benefit ends if you die or regain consciousness.

Essence Theft

Starting at 1st level, your necromancy spells leaves a mark on the creatures they hit. You can use your bonus action to touch a marked creature and consume the mark, gaining a number of  hit points equal to your Proficiency bonus, the touched creature will receive the same amount as necrotic damage.

You can consume an amount of marks equal to your Charisma modifier. You will need a long rest to regaing the expended uses.

Necrocaster

Starting at 6th level, your necrotic powers flow from within you with increasing intensity. Choose one 1st level necromancy spell that you already know. You can cast that spell at it lowest level without expending a spell slot. If you want to cast that spell at a higher level, you must expend as many sorcery points as spell level.

Borrowed Life

Starting at level 14, you gain resistance to necrotic damage.

Additionally, if a creature has beed dead for less than an hour, you can use you action to touch it and do one of the followings:

• Drain its soul to regain as many hit points as the creature's half maximun hit points. 
• Summon their soul as a specter which is under your control. The specter has its turn just after yours and will obey your command until the next long rest. After that, it will vanish to the after life. You can communicate with it even if you both dont speak the same lenguage.

You will need a long rest or spend 5 sorcery point to use this trait again.

Life Swap

By reaching level 18, you have developed your necrotic powers enough to change the fate of the creatures around you. You can use your action to target a creature you can see that is within 30 feet and force it to make a Constitution saving throw. If it fails, you exchange current hit points with the creature you chose. It will have as many hit points as you had, and you will have as many hit points as its had. If successful, it will negate the life swap and become inmune to it for 24 hours. The creature you choose can choose to fail.

After using this trait, you will need a long rest to use it again.