Ethereal Magic

Your innate magic comes from the Ethereal plane manifesting in ghostly ways. You might trace your lineage to an entity from the Border Ethereal, or perhaps you were exposed to its the gloom of the Deep Ethereal and molded by it.

The power of ethereal magic casts a strange pall over your physical presence. The spark of life that sustains you is not your own, as if you are possessed by another being. This could manifest in any number of ways. Perhaps you hear the voice of the entity that possesses you, or maybe you are the entity and the voice you hear is your own. You're hair might float as though your a drowned spirit, or maybe you appear vaguely translucent in sunlight. There's any number of ways your powers might physically manifest.

Ghostly Vision

Starting at 1st level, you have darkvision with a range of 120 feet.

When you reach 5th level in this class, you learn the blink spell, which doesn’t count against your number of sorcerer spells known. In addition, you can cast it by spending 3 sorcery points or by expending a spell slot. If you cast it with sorcery points, you have full control of the ethereal magic and can shift back and forth to the ethereal plane at will for the duration of the spell at the end of your turn.

Drain Life

Starting at 1st level, the essence of the ethereal plane allows you to drain the life of another. Once per long rest, you may make a special melee spell attack. 

On hit, the target takes 3d6 necrotic damage. Additionally, the target must succeed on a Constitution saving throw equal to your spell save DC or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the creature finishes a long rest. If the target has its hit point maximum to reduced 0 by the attack, it dies and you gain temporary hit points equal to the damage dealt.

After you use this feature, you can’t use this feature again until you finish a long rest.

Incorporeal Phantom

At 6th level, you gain the ability to call forth a spectral creature of unlife to assist you. As a bonus action, you can spend 3 sorcery points to magically summon an incorporeal phantom to assist you. You can cause a spirit to exit your body as a specter, the statistics for which are in the Monster Manual. When the specter appears, it gains temporary hit points equal to half your sorcerer level rounded down. Roll initiative for the specter, which has its own turns. It obeys your verbal commands, and it gains a special bonus to its attack rolls and armor class equal to your Charisma modifier (minimum of +0).

The specter remains in your service until the start of your next long rest, until it reaches 0 hit points, or until you dismiss it as an action, at which point it returns to your body.

Once you summon an incorporeal phantom with this feature, you can’t use the feature again until you finish a long rest.

Incorporeal Movement

At 14th level, you gain the ability to adopt an incorporeal form and stride through the world.  You can spend 1 sorcery point per round as a bonus action to move through other creatures and objects as if they were difficult terrain. You take 1d10 force damage if you end your turn inside an object or creature and remain there until you move at the start of your next turn. If this damage reduces you to 0 hit points, your physical form is shunted to a random unoccupied space. 

Possession

Starting at 18th level, you can spend 9 sorcery points as a bonus action to magically transform yourself into a ghostly being, and attempt to possess a humanoid once per long rest. One humanoid that is not undead that you can see within 5 feet of it must succeed on a Charisma saving throw against your spell save DC or be possessed by you; you then disappear, and the target is incapacitated and loses control of its body. You now control the body but doesn't deprive the target of awareness. You can't be targeted by any attack, spell, or other effects, except ones that turn undead, and you retain your alignment, Intelligence, Wisdom, Charisma, any immunities to being charmed and frightened. You otherwise use the possessed target's statistics, but don't gain access to the target's knowledge, class features, or proficiencies. The humanoid you possess can still be targeted by attacks, spells, and other effects that would normally affect them. (I.e. A spell like mind spike would affect the mind of the humanoid you possess, but not you.)

The possession lasts until the body drops to 0 hit points, you end it as a bonus action, or you are turned or forced out by an effect like the dispel evil and good spell. When the possession ends, you reappear in an unoccupied space within 5 feet of the body. The target is immune to your Possession for 24 hours after succeeding on the saving throw or after the possession ends.