Your powers are like that of a creature of shadow, for your innate magic comes from the Shadowfell itself. You might trace your lineage to an entity from that place, or perhaps you were exposed to its fell energy and transformed by it. The power of shadow magic casts a strange pall over your physical presence. The spark of life that sustains you is muffled, as if it struggles to remain viable against the dark energy that imbues your soul.
At 3rd level, your eyes adapt to be able to see in the dark. You have darkvision with a range of 60 feet. You also learn the darkness spell, which doesn't count against your number of sorcerer spells known. In addition, you can see through the darkness created by the spell.
Additionally, your can add your Charisma modifier to the damage of spells that deal necrotic damage.
Starting at 1st level, your existence in a twilight state between life and death makes you difficult to defeat. When damage reduces you to 0 hit points, you can make a Charisma saving throw (DC 5 + the damage taken). On a success, you instead drop to 1 hit point. You can't use this feature if you are reduced to 0 hit points by radiant damage or by a critical hit.
After the saving throw succeeds, you can't use this feature again until you finish a short rest. You can spend 3 sorcery points to use this feature again when you have no uses remaining.
At 6th level, you gain the ability to call forth a howling creature of darkness to harass your foes. As a bonus action, you can spend 3 sorcery points to summon a hound of ill omen to target one creature you can see within 120 feet of you. The hound uses the dire wolf's statistics, with the following changes:
The hound is size Medium, not Large, and it counts as a monstrosity, not a beast.
It appears with a number of temporary hit points equal to your sorcerer level.
It can move through other creatures and objects as if they were difficult terrain. The hound takes 5 force damage if it ends its turn inside an object.
At the start of its turn, the hound automatically knows its target's location. If the target was hidden, it is no longer hidden from the hound.
The hound appears in an unoccupied space of your choice within 30 feet of the target. The hound takes its turn at the same time as you. On its turn, it can move only toward its target by the most direct route, and it can use its action only to attack its target. The hound can make opportunity attacks, but only against its target. Additionally, while the hound is within 5 feet of the target, the target has disadvantage on saving throws against any spell you cast. The hound disappears if it is reduced to 0 hit points, if its target is reduced to 0 hit points, or after 5 minutes.
At 14th level, you gain the ability to step from one shadow into another. When you are in dim light or darkness, as a bonus action, you can teleport up to 120 feet to an unoccupied space you can see that is also in dim light or darkness. After you teleport this way, your next spell attack roll has advantage.
Starting at 18th level, you can spend 6 sorcery points as a bonus action to transform yourself into a shadowy form. In this form, you have resistance to all damage except force and radiant damage, and you can move through other creatures and objects as if they were difficult terrain. You take 5 force damage if you end your turn inside an object.
You remain in this form for 1 minute. It ends early if you are incapacitated, if you die, or if you dismiss it as a bonus action.