Specter

You know how to use your soul's relationship with the Ethereal Plane to walk in between this plane and the next. Maybe you were born in the plane of ghosts, or perhaps something went wrong when you were resurrected, and a part of you is still there. Specters dance through their enemies and solid objects, waltzing in and out of the Ethereal Plane with the same effort as passing through an open door.

Sharp Shadow

At 3rd Level, you’ve learned to fight by phasing through your enemies. You gain a special melee attack with a range of 5 ft. Instead of rolling to hit, this attack forces the target to make a DEX saving throw equal to your Spector Save DC. On a failure, the target takes 1d6 + your Constitution modifier in force damage and you teleport to an unoccupied space within 5 ft of the target. On a success, the target takes no damage and you still teleport. You can only take this special attack once per turn.

When you use your Action Surge feature, you can use this attack twice for that turn. When you use Sharp Shadow in this way, a creature takes half damage on a successful DEX save, instead of no damage as normal.

Spector save DC = 8 + your proficiency bonus + your Constitution modifier.

Visitant Body

At 3rd level, As an action on your turn, you can go halfway between the Ethereal Plane and this one allowing you to walk through some solid objects and creatures. If the creature or object has an AC equal to 12 + your Constitution modifier or lower, you can move through it. You can find rules for the AC of objects in chapter 15 of the basic rules.

Moving through solid objects or creatures is considered difficult terrain, and every 5 ft of movement deals 1d6 force damage to you unless that creature is nonhostile to you. If you drop to 0 hit points during this time, you are forced to the nearest unoccupied space.

Your body is in this form for 10 minutes, unless you end it early as a bonus action. Once you use this feature, you must finish a short or long rest before you can use it again.

Transparency

At 7th level, You can now see into the Ethereal Plane. Being able to see other creatures’ souls gives you a knack for insight, you have advantage on insight checks.

Additionally, while your Visitant Body feature is active, you have a flight speed of 10ft and can hover. 

Displace

At 10th level, you can blur the line between being tangible and incorporeal. You have an amount of charges equal to your Constitution modifier (a minimum of one). You can cast the Blur and Pass Without Trace spells by expending a charge. You regain all expended charges when you finish a long rest.

Phantom

At 15th level, You can be a spirit residing halfway between your current plane and the Ethereal Plane. While you are at full hit points, you can cast the Blink spell, and the spell does not end until you take a long rest or you are no longer at full hit points. When you are in the Ethereal Plane in this way, creatures in the current plane can hear you, and creatures who are familiar with you can see a ghostly outline of you. While this spell is active, you cannot go through solid objects in either plane unless your Visitant Body feature is also active.

Possession

At 18th level, you can attempt to control a creature by possessing them. If you are within 5tft of a humanoid, you can use your action to force that creature to make a Charisma saving throw with a DC equal to your Spector save DC or be possessed for 1 minute. A creature automatically succeeds this saving throw if the creature is a construct or is immune to being charmed. The target is considered incapacitated for the duration. You must concentrate on this possession as if concentrating on a spell. You end the possession early if you use your Sharp Shadow feature, Visitant Body feature, if the target drops to 0 hit points, or if you lose concentration. Your concentration on the possession is not affected by your body taking damage, but rather if the target takes damage. The target can repeat the saving throw at the end of each of your turns, ending the possession on a success.

For the duration, Your body goes prone and you are considered Blind, Deaf, and Paralyzed. When the possession ends, your spirit is transported to your body. Your body decays without a spirit dwelling in it, at the end of each of your turns your body takes 1d12 necrotic damage. This damage can't be reduced or prevented in any way. If your body gets to 0 hit points, the possession ends, and you die outright as your spirit is banished to the Ethereal Plane.

During this time, you use the possessed target's Statistics, but you don’t gain access to the target's knowledge, Class Features, Proficiencies, or mental stats, but you retain your own. 

You can use this feature once per long rest.