Pact of the Abyss

With god gone, his home was empty, leaving a space for him to fill in. Knull, the nameless, emperor of the abyss took control of god's home. The spreading emptiness poured down into the heavens in the form of rain of nothingness. The angels created a vast system of aqueducts to move the void matter down to the layers of hell. Hell is slowly becoming consumed by the void, creatures of Knull's design taking over hell one creature at a time.

Level 3: Abyssal Mark

Your arm is consumed with void matter, cost of the deal. Your arm is as it usually is but pitch black. Your unarmed strike now deals cold damage. You form a symbiotic relationship with the void matter, it growing as you do.

You are able to transform it into different things and use it to deal devistating blows against your enemies.

Level 3: The Ghost, The Demon, and The Angel

You are able to switch which Abyssal energy you channel.

The Ghost, slender, quick, agile, and cunning. This energy typically has long skinny limbs and is a very unstable form, causing dripping void matter to collect in a puddle beneath it. The Ghost is known for getting places it shouldn't, being able to pass through matter and fall into it's own puddle.

The Demon, crazy, mad, insane, and above all strong. This energy is large and "muscular" with pointy angles, spikes, and horns. The Demon is known for it's incredibly strength, and terrifying nature. Approach with extreme caution.

The Angel, graceful, resourceful, intelligent, and arcanically blessed. This energy looks as though it was made with metal meant to look like bones. The Angel is known not only for it's wings and flying capabilities, but also the it's gift of magic.

Mutation

You can manipulate your Abyssal mark to change the properties of you inflicted arm. These properties depend on your current Abyssal energy.

Ghost.
+1 in Dexterity when using the inflicted hand.
Intangible. You can move your arm through solid matter as long as it is less than 6" thick (half a foot). You cannot bring matter back through.
Action - Abyssal Swipe. Proficient. +DEX Modifier to hit. Reach. Upon a succesful hit, the target must make a succesful CON Saving Throw of DC 12 or they become paralysed until they can succeed the check. They can reroll every turn.

Demon.
+1 in Strength when using the inflicted hand.
Cold Grasp. Whenever you have a creature grappled with the hand, the creature takes 1d6 Cold damage at the end of their turn if they do not escape.
Action - Abyssal Claw. Proficient. +STR Modifier to hit. Reach. Deals 1d8 Cold damage.

Angel.
+1 in Charisma Modifier when using the inflicted hand. 
Empty Arcana. Whenever you touch anything magical with your hand, as long as you are touching it, it loses all function. You are also unable to activate glyphs you did not write.
Reaction - Shutdown. Whenever a ranged projectile spell is cast at you, roll a DEX saving throw. If the result is higher than the caster's roll to hit, you catch it and deactivate it.

Level 6: Abyssal Cloak

Gain the Ability to cloak yourself in the void matter, giving you abilities based on your Abyssal Energy.

Ghost:
Same bonuses as Mutation.
Gain Advantage in Dexterity Saving Throws.
Resistance to Cold Damage.
Advantage on Stealth.
Attacks of opportunity made against you have disadvantage.
You gain darkvision of 60ft.
You are unable to make sound.

Demon:
Same bonuses as Mutation.
Gain Advantage in Strength Saving Throws.
Resistance to Cold Damage.
Advantage on Intimidation.
You gain multiattack on Abyssal Claw.
You are able to sense creatures within 10ft of you, knowing their location without needing sight.
You are unable to speak, just growl and scream.

Angel:
Same bonuses as Mutation.
Gain Advantage in Charisma Saving Throws.
Resistance to Cold Damage.
Advantage on Arcana.
You gain 3 temporary spell slots. (This feature cannot be used again between long rests.)
You gain 20ft of flight speed.
You are able to speak fluent common and any other languages you normally know.

Level 10: Abyssal Form

Once per long rest, as an action, you can transform your entire being into an Abyssal form. You can dispell this form as an action. If your hit points drops to 0, you immediately dispell the form. You are unable to swap between energies while in form. You gain temporary hit points equal to half your typical hit points. However, if you get hit by a critical hit, it affects both your usual health points, and your temporary hit points. However, such a powerful form places strain on the body. Every time you end your turn still in Abyssal form, roll a CON saving throw of DC 12, on failure, take 1d8 Cold damage.

The Ghost:
All bonuses as Mutation and Cloak, but +2 to DEX increase as well as additional +1 DEX for all checks and attacks. (Doesn't stack).
Your temporary hit points are halved upon first taking damage.
You can move through walls as long as there are holes in the wall of decent size.
You make no sound while moving.
All attacks of opportunity made against you automatically fail.
Void Blade. Make an attack with your weapon as you would normally. This weapon does the damage once using the normal damage type, and the same amount of damage again but dealing cold damage. Dealing a critical hit does double the normal damage and double the cold damage.
Abyssal Well. As a bonus action, you can melt your form into the pool of void matter beneath you. In this form you are unable to interact with the environment, including attacks and spells. You are also able to move under and through things as water would. You return to normal at the end of your turn.

The Demon:
All bonuses as Mutation and Cloak, but +2 to STR increase as well as additional +1 STR for all checks and attacks. (Doesn't stack).
Your AC is set to 20, regardless of armour or Dexterity.
You have advantage on grappling, and cannot be grappled.
You cannot be moved unwillingly.
Abyssal Claw deals double the usual die value.
Abyssal Slam. Make an unarmed strike attack. This attack deals 2d10 bludgeoning damage. The target is knocked prone. This does double damage if you are atleast 20ft in the air.
Leap of Might. As a bonus action, you are able to leap 20ft up and 30ft across.

The Angel:
All bonuses as Mutation and Cloak, but +2 to CHA increase as well as additional +1 CHA for all checks and attacks. (Doesn't stack).
You gain fly speed equal to your walking speed.
All your damage spells deal Cold damage.
You are immune to being Charmed.
You gain 5 temporary spell slots that are of any level you want.
Abyssal Smite. Proficient. Smite a single target with the wraith of the void. 2d8 Cold Damage. Creature can make a CON Saving Throw of DC 16 to half the damage.
Void Blink. As an action, teleport to any unoccupied space within 20ft of you. Recharges if you do not use any movement speed for a turn.

Level 14: Void Domain

Once per long rest, you can call upon the power of the void to have it rain void matter. Void matter covers a 50ft area around you, about an inch or two deep. You can summon 4* void tendrils to burst out anywhere in the 50ft area. You can attack with 2* of these tendrils per turn as a bonus action. These tendrils can attack with +6, dealing 1d10 Cold Damage on a succesful hit. Additionally, while in form, you gain the following benefits.
Ghost - Double movement speed while using Abyssal Well.
Demon - Heal 1d8 temporary hit points when ending your turn standing in the matter, at the cost of taking 1d4 Cold damage directly.
Angel - Increase spell radius when the spell lands in the void matter by an additional 5ft. (20ft range -> 25ft range.)

*At level 16, this goes up to 6 and 3 respecitvely.

The effects of Void Domain doesn't go away unless you use an action to dismiss it, of which it will slowly dismiss over 24 hours.