The spirits of the departed can linger after their mortal death when there is some important unfinished business, or be summoned into servitude by powerful necromancers. The unfinished business of ghosts can take many forms; protecting loved ones, guarding a valuable item, or revenge upon an old enemy. An awakened ghost might find that the death of their master has released them from service, or the business they've left unfinished in life may take them far and abroad to complete, or they simply cannot find their way into the afterlife, and have embraced their new undead existence.
Ghosts are ethereal, glowing with spectral light. While ghosts still have substance, it is that of an energies and particles closely resembling that of a gaseous form. Ghosts have limited abilities in interacting with the physical plane - they can move small objects and interact with creatures and items. Ghosts tend to maintain a reflection of what they looked like in their past life; wearing armor or clothes they died in, having a spectral reminder of weapons or jewelry they once wore, but these are little more than manifestations. They also will bear the scars of their death - obvious and twisted marks that the living often find deeply disturbing. A ghost who once drowned might be caked in seaweed and spectral sea creatures that crawl on their form, or a murdered soul might have gaping wounds that always appear to be bleeding.
Ability Score Changes
Your Strength score becomes 7. Your Charisma score increases by 3, to a maximum of 20.
Disembodied Existence
Your lack of physical cohesion makes it very difficult to hurt you. You gain resistance to acid, fire, lightning and thunder damage, as well as attacks from non-magical bludgeoning, piercing and slashing attacks. You are also immune to cold damage. It is also impossible to grapple you, knock you prone, or otherwise restrain you. You can still manipulate objects, open unlocked doora or containera, stow or retrieve an item from an open container, or pour the contents out of a vial. Although you may appear as though you have the equipment you had in life, you can't wear or gain benefits of armor, wield weapons, or activate magic items, or carry more than 10 pounds.
Ethereal Sight
You exist on the border between the Ethereal Plane and the Material Plane. Because of this, you can see 60 feet into the Ethereal Plane when you are on the Material Plane, and vice versa.
Spectral Movement
You no longer truly walk, swim, climb or burrow. Your spectral nature means you are always floating, or flying. You gain a fly speed of 50 feet.
Incorporeal Passage
Your bodiless nature allows you to pass through physical objects with little difficulty. You can move through other creatures, objects and non-magical physical barriers as if they were difficult terrain. You take 1d10 force damage if you end your turn inside an object. If you end your turn inside a physical barrier, you take 4d10 force damage and are ejected to the nearest free space.
Withering Touch
Though your ghostly remains may still carry reminders of the weapons you once wielded in life, your weapons are no more than ghostly manifestations. You might appear to attack with your hand, or what looks like a sword or axe, but the effect is always a Withering Touch. Your weapon attacks are replaced with this feature, and your unarmed strikes now deal necrotic damage. As an action, you make a melee touch attack and deal Necrotic damage equal to 2d6 + your Dexterity modifier. This damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level.
Horrifying Visage
Starting at 6th level, as an action you can use your spectral horror to strike fear into your enemies. Each non-undead creature within 60 feet of you that can see you must succeed on a Wisdom saving throw equal to 8 + your Charisma modifer + your proficiency bonus or be frightened for 1 minute. If the save fails by 5 or more, the target also ages 1d4 × 10 years. A frightened target can repeat the saving throw at the end of each of its turns, ending the frightened condition on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune this feature for the next 24 hours. The aging effect can be reversed with a greater restoration spell, but only within 24 hours of it occurring.
Once you use this feature, you can't use it again until you finish a short or a long rest.
Etherealness
Starting at 11th level, you learn to move yourself between the planes you exist between. You can move to the Ethereal plane to bypass barriers and obstacles on the Material Plane with ease. As an action you can enter the Ethereal Plane from the Material Plane, or vice versa. You remain visible on the Material Plane while in the Border Ethereal, and vice versa, yet you can't affect or be affected by anything on the other plane.
Possession
At 16th level, you've become so powerful you can possess the bodies of living creatures. You can target one humanoid that you can see within 5 feet of you. The target must succeed on a Charisma saving throw equal to 8 + your Charisma modifier + your proficiency bonus 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 this doesn't deprive the target of awareness. You can't be targeted by any attack, spell, or other effect, except ones that turn undead, and you retain your alignment, Intelligence, Wisdom, and Charisma. You otherwise uses the possessed target's statistics, but don't gain access to the target's knowledge, class features, or proficiencies.
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. You cannot use this feature again until you finish a long rest.