Age
Most Shadows Demons are 10,000+ and they can't truly be killed but might choose to pass on at some point

Ability Score Increase
Your Dex increases by 3.
Your Con increases by 2.
Your Cha increases by 1.

Size
You are medium for the reason of "having a human-like a skinsuit" That you shift in and out of.

Shade Rend
Harden shadow to form a body as well as items

Speed
Your base walking speed is 30 ft.

Condensed Darkness
Shadow's don't need to sleep. Instead, they rest similar to elves, but instead of meditating they must sit down, preferably in darkness, for 3 hours a day.

Amorphous

You can move through any opening the size of 1 inch wide without squeezing.

Keeper of knowledge
Because you have been around for so long you have picked up a few "techniques" in doing so you have had time to learn and study all the languages in the world and due to that you can read and speak all languages.

Combat abilities
You have great proficiency with the melee weapons and attacks.

Once a man, Always a Demon
You gain racial proficiency in Arcana, Deception, Insight, and Stealth.

Deadlier Than the Sun, or Stronger Than the Earth?
While your immune to necrotic, you are vulnerable to radiant.

Being a shadow, it is hard to hurt you with normal attacks. you have resistance to Acid, Cold, Fire, Lightning, Thunder, Necrotic, Poison, and Bludgeoning, Piercing, and Slashing from Nonmagical Attacks, and vulnerability to Radiant damage.

Lastly, you are immune to these conditions: Exhaustion, Grappled, Paralyzed, Petrified, Poisoned, Prone, Restrained, Blinded.

Darkvision
You have superior vision in dark and dim conditions. You can see in dim light within 60 ft. as if it were a bright light, and in darkness as if it were dim light. You can unlike most with this ability discern color in darkness, not just shades of gray.

shadows acrobatics
advantage when rolling acrobatics, while no it direct sunlight.

Multiattack. The demon makes two claw attacks.

Shadow Stride
A Dark Shadow of 8th level or higher can vanish from his current location and reappear in any shadowy area within 90 feet. This is a move-equivalent action.

Shadow Stealth
While in dim light or darkness, the demon can take the Hide action as a bonus action.

Shadowed Armor
Shadows are difficult to hit in shadow, and as a result, gains a +2 to their armor class while in darkness.

Shadow Magic Initiate
The Dark Shadows innate spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). The Dark Shadows can innately cast the following spells, requiring no material components:

At will: detect thoughts, disguise self, mage hand, minor illusion

3/day each: charm person, detect magic, invisibility, major image, suggestion

1/day each: dominate person, fly, plane shift, true seeing

Shadow Knights Arsenal

All of your character's weapons are transformed into shadows and absorbed into your bodies shadow realm allowing you to summon them at will.

Shadow Realm

You are able to use your shadow realm to store anything within you similar to the way your weapons are stored but with this, you can change them back

Ranged Shadow attacks

At 7th You are able to shoot shadow blades from any shadow within view

Deaths Door
At 10th Allows you to pull souls from the afterlife and tether them to either homunculi or a body of your choosing.