Shadow Arm.

The Shadows have whispered to you of their power, offering you their strength and control... for a price. Taking hold of the power of the Shadows themselves is no small cost indeed. When you cut the deal, you offer up one of your arms in payment to the living shadows for them to bind themselves to you. Once the Shadows have consumed your arm they leave behind a small sign of your bond, in the form of the semi-living tendrils of dark smoke and mist that now cascades down from the shoulder of your missing limb.  Yet this is not a one way arrangement, the Shadows that now share your body bring many gifts with them; the ability to re-forge what you lost into a deadly weapon, bestowing dark magics, and making you almost nigh impossible to touch. As your bond grows and strengthens, you will embody what it is to be a harbinger of darkness.

Shadow Claw

3rd-level Shadow Arm Feature

As a Bonus Action you are able to cause the shadows to gather and form a wicked clawed arm in place of the one you gave up. This new arm acts as a natural weapon that uses your Dexterity for Attack and Damage, dealing 1d4 necrotic dmg, with a reach of 10 feet. You can do this a number of times per long rest equal to  your constitution modifier, this effect last for 10 mins per use unless you are incapacitated, if you die, or if you dismiss it as a bonus action. Alternatively, you can cause the shadows to shield you momentarily. As a reaction to being hit with an attack, you may dismiss your Shadow Arm for a bonus to your AC for that attack equal to your Constitution bonus, potentially causing the attack to miss you.

As you gain levels and your bond grows, your claws become an ever increasingly deadly weapon.
- At 7th lvl: The Damage becomes 2d4 and you gain a +1 to Attacks made with Shadow Claws.
- At 10th lvl: You gain a +2 to Damage rolls made with your Claw Strikes and attacks made with your claw ignore resistance to Necrotic Dmg.
- At 15th lvl: The Damage becomes 3d4 and you gain an additional +1 to Attacks made with Shadow Claws.
- At 18th lvl: The Damage becomes 4d4 and your Claw Strikes Crit on rolls of 18-20.

Gifts of the Dark

3rd-level Shadow Arm Feature

The sacrifice of your arm brought both gifts and hinderances. The shadows have gifted you with some of their innate magics. Bestowing upon you twisted versions of the Chill Touch and Mage Hand cantrips. Your spell casting ability for this is Constitution.

- For you the Chill Touch cantrip no longer requires verbal or somatic components but the range is only 30ft
- Similarly, Mage Hand no longer requires verbal or somatic components and the hand is made of opaque swirling shadows.

However, due to your missing appendage, you find difficulty with certain tasks. You have disadvantage on Athletics and Acrobatics checks for things such as Climbing and Grappling.

Shadow Skills

7th-level Shadow Arm Feature

The shadows themselves are now drawn to you, helping to obscure your movements and actions.

You gain Proficiency in Slight of Hand and Stealth. If you are in Dim light or Darkness, you have advantage on Stealth Checks.

Shadow Shroud

10th-level Shadow Arm Feature

As your bond with the shadows deepens, you are able to wrap your entire body in the living darkness.

You are able to command the shadows to blur your form, making it harder for your enemies to hit you.
- You gain the ability to cast Blur a number of times per long rest equal to your Constitution Modifier

Shadow Rend

15th-level Shadow Arm Feature

The shadows you command feed off of many things in this world and now you reap a piece of these rewards. You are able to steal a portion of life from your enemies when your shadow claws tear into them.

Once per turn when you hit a creature with a Claw Strike, you are able to perform a Shadow Rend.
- Shadow Rend deals and extra 6d4 necrotic damage and you regain Hit points equal to half of the total damage dealt (Rounded up) from the attack. Alternatively if the total damage dealt would kill the creature, you instead regain hit points equal to the full amount of HP they had left. (ex. a creature with 10 hp left when it died, you would only gain 10 HP. A creature with 30 hp left when it died, you would gain all 30 hp. Even if you dealt 35 points of damage with the attack.)
- You are able to use Shadow Rend a number of times equal to half your proficiency bonus (rounded down) per long rest.
- Killing a creature with Shadow Rend causes the creation of a Shadow. Raising from the remains on the next sunset.

Shadow Armor

15th-level Shadow Arm Feature

The shadows snap and writhe even more energetic than before, making it harder for enemies to land blows against you.

While you have Shadow Claw activated, you gain +1 bonus to your AC.

Shadow Form

18th-level Shadow Arm Feature

Your bond and understanding of the Shadows that share your body has become great indeed, allowing you to not only pull the shadows to you but into you as well. For a short time you infuse your body with these shadows to take on this new form. You become partially insubstantial moving and flowing as the shadows do, making you quicker, tougher, and almost impossible to pin down.

When you shift into Shadow Form as a Bonus action, Shadow Arm and Shadow Shroud both activate without expending a use. You are able to use this feature a number of times equal to half your proficiency bonus per long rest, lasting for 1 min and gaining the following effects.
- You gain Resistance to all damage types except for Radiant, Fire and Lightning. Instead becoming vulnerable to these damage types. 
- You become quicker and harder to pin down. Your walking speed increases by 5 feet and you have advantage on Dexterity saving throws.
- You ignore difficult terrain and can move thru spaces occupied by hostile creatures, you take 5 force damage if you end your turn inside an object