Your dark magic comes from the Adverseric magic that was infused with your blood from your day of conception. Most often, sorcerers with an Adverseric bloodline trace their descent back to The Adversary in one way or another; most of these bloodlines are established in places other than this world, mostly dwelling in the etheric rifts between dimensions.

Adverseric Spirit

Adverseric Ancestry 

At 1st level, you choose your ancestral spirit, the ancestral spirit you choose will grant access to different features you will gain later.

Spirit	DAMAGE TYPE
Black	Necrotic
Golden	Radiant
Red	Fire
Silver	Ice

 

Black Soul

The darkest of dark magic users come from those with the darkest of souls...

Golden Spirit

Those with Golden Spirits are those of pride and justice.

Red Spirited

Those who run hot blooded with rage in their heart(s).

Silver Heart

Those with hearts full of sorrow and remorse for their families wrong doing.

Spiritual Resistance

The Affinity of your spirit grants you a resistance based on what you choose. 

Spiritual Strike

Starting at 6th level, when you cast a spell that is the same damage type associated with your ancestral spirit, you can add your Charisma modifier to one damage roll of that spell or you can spend 1 sorcery point to gain resistance to that damage type for 1 hour.

Spirit Burn

The strength of your spirit is stronger than many of your opponents. If you kill an opponent with the magic of the same type as your soul you gain back a sorcery point. 

Adverseric Presence

Beginning at 18th level, you can channel the dreadful presence of your Adverseric ancestor, causing those around you to become awestruck or frightened. As an action, you can spend 5 sorcery points to draw on this power and exude an aura of awe or fear (your choice) to a distance of 60 feet. For 30 minutes 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 charmed (if you chose awe) or frightened (if you chose fear) until the aura ends. A creature that succeeds on this saving throw is immune to your aura for 24 hours.