Ghost Assassin

Ghost assassins are firm believers that life is for the living. The living should make the most of their lives and pursue what they want while they've still got time, and find their own peace before death. If you die with unfinished business, well, that's probably your fault. And if it's not...perhaps they could help you...for a price.

Ghostly Weapons

At 3rd level, you can once per short rest turn your melee weapons incorporeal for 1 minute. Your attacks ignore all resistances undead creatures have. As well your attacks disrupted the living causing additional necrotic damage equal to your proficiency bonus to non undead and non construct creatures.
This feature can be used twice per short rest at level 9, three times per short rest at level 13 and four times per short rest at level 17.

Spirit Lore

When you choose this archetype at 3rd level, you gain proficiency in the Religion skill if you don't already have it. You add double your proficiency for this skill.

Shadeskin

Beginning at 9th level, you can once per long rest you can turn yourself incorporeal for up to 1 minute. You gain resistance to: Acid, Cold, Fire, Lightning, Thunder; Bludgeoning, Piercing, and Slashing from Nonmagical Attacks while incorporeal. You can also 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. Dismiss as a bonus action.
You can use this feature twice per long rest at level 17.

Spectral Strike

Starting at 13th level, while you or your weapons are incorporeal and you make an attack that qualifies for your Sneak Attack feature you can instead cause the target to make a Dexterity saving throw, DC equal to 8 + your Proficiency modifier + your Dexterity modifier. On a failure the target takes damage as if you had successfully made an attack plus the damage from your Sneak Attack feature. Damage dealt from this feature ignores resistances.

Ghost Step

Starting at 17th level, you can once per long rest you may cast the Etherealness spell at 7th level as a ritual.