Whether your family recived a cursed or one of your ancestors became a Lich, you were born with the capability with using magic similar to that used by undead creatures, your abilities allow you to do things that are beyond the limit of what a humanoid can do with magic of the school of necromancy. As expected from the origins of your abilities you can manipulate the dead using your magical abilities, you are capable of raising the undead and rule over them, as well as using the powers of certain undeads by yourself.

Extended spell list

At 1st level, you start learning new spells as you level up

Sorcerer level	Spells learned
1st	Cause fear, Inflict Wounds
3rd	Gentle Repose, Ray of Enfeeblement
5th	Revivify, Bestow Curse
7th	Shadow of Moil
9th	Danse Macabre, Negative Energy Flood

Undead transformation

The curse that affects you prevents you from dying under most circumstances, when your hp hits 0, if you dont outright die and this wasnt caused by radiant damage, instead of falling unconcious you transform into a zombie like crature, your creature type becomes undead, you become resistant to necrotic damage and can add a d6 of necrotic damage whenever you inflict damage to a creature, your charisma modifier swaps place with your strenght modifier and you become unable to cast spells that have a range other than self. In this form your hit dice is a d8 instead of a d6, this form lasts until you are affected by a spell of with the ability to revive creatures or you kill another creature, you loose all proficiencies that you may have and all class features that arent specified as compatible with undead form. If a spell or class feture that affects undead requires a DR yours is your proficiency bonus plus half your sorcerer level.

Voice of the dead

Starting at 6th level, you can spend one sorcery point to casr speak with dead without expending a spell slot or material components, if you are in undead form you can do it for free.

Spells from the grave

At 14th level, when you use any damaging spell from the necromancy school, deals necrotic damage or that targets undead you can spend 2 sorcery points to max deal maximum damage instead of roling

Undead proficiencies

Beginning at 18th level, you become an expert at using your undead form, as an action you can spend 4 sorcery points totransform into your undead form, when you enter undead form this way you gain proficiency with shields, simple weapons and weapons with the heavy feature, you also gain advantage on death saving throws