Lich Ancestry

Your innate magic comes from the Lich's Curse that has affected your bloodline.  Sorcerers of this type usually appear gaunt and sickly though they are usually more hearty than other sorcerers besides, perhaps, the Dragon Blooded.  Most of these bloodlines can be traced back to ancient liches that dabbled in dark arts they shouldn't have, but some can be traced back to famous liches such as Vecna.  Lich Ancestry sorcerers have a high propensity towards undeath and an uncanny control over necromantic magic, making them formidable allies and frightening enemies.  

Lich's Ancestral Curse

Because of the Lich's Curse, you have shown a propensity for undeath.  Your features are more gaunt than that of someone not of this bloodline.  In addition, when selecting spells, you may select from any spell with the Necromancy type.  

Because of your Necromantic abilities, you may force an undead you can see that has a CR up to your caster level divided by four to roll a WIS save.  This save is equal to your spellcasting modifier.  If the undead fails, they fall under your control.  At the end of one minute, they may re-attempt the save.  If they fail the second save, they are under your control for 24 hours after which you permanently lose control of the undead creature.  

Undead Constitution

As magic flows through your body, it causes physical traits of your ancestral lich's curse to emerge. When rolling HP at level up, you may add your CON modifier twice to your HP pool.

Additionally, you have seen things car scarier than any normal person.  Fear no longer holds sway over you and you are immune to both magical and non-magical fear effects.

Necrotic Affinity

Starting at 6th level, when you cast a spell that deals necrotic damage, you can add your Charisma modifier to one damage roll of that spell. At the same time, you can spend 1 sorcery point to make a pact with the creature as it dies.  The creature arises as a Deathlock Wight (MToF129) until it dies.  This creature goes on its own initiative and will follow the last command it was given until it dies or the command has been completed.  You may give a new command as a bonus action on your turn.  Outside of combat, you may command it to perform simple tasks (i.e. open/close doors, pick up small items, etc) and it will follow you unless commanded to stay in a location.

You may have a number of Deathlock Wights active equal to half of your proficiency bonus rounded down.

Shroud of Undeath

At 14th level, you gain the ability to veil yourself with a necrotic shroud at the cost of your own life force, gaining a flying speed equal to your current speed. You can create or this shroud as a bonus action on your turn. It lasts until you dismiss it as a bonus action on your turn.

While the shroud is active, enemies attacking you do so with disadvantage.  However, due to the drain on your life force, you lose HP equal to your CON modifier each round this shroud is active.

 

Lich's Visage

Beginning at 18th level, you can channel the dread presence of your Lich's curse, causing those around you to become or frightened. As an action, you can spend 5 sorcery points to draw upon undeath and exude an aura of fear for a distance of 60 feet. For 1 minute or until you lose your concentration (as if you were casting a concentration spell), each hostile creature that starts its turn in this aura must succeed on a Wisdom saving throw or be frightened until the aura ends. A creature that succeeds on this saving throw is immune to your aura for 24 hours.  If a creature under the frightened condition dies within the aura, you may choose to raise them as a Deathlock Wight.  This ability cannot cause you to exceed the maximum number of wights you may have active.

While this ability is active, you appear as though you were a Lich.  Your appearance returns to normal once the effect ends.