Pact of the Shattered Chain

The most common form for this pact to take is rare by itself, for the process is one that can only be wrought by mortal hands. When a demon is killed outside of the Abyssal plane, it attempts to regenerate within its native realm; when the magics of mortals interfere with this, what is created is a Shadow Demon. A portion of the demon's power and soul, given form once more, but cut off entirely from the Abyssal plane. Such an existence is hollow and empty, and the demon does much to find itself a new protector, someone who can keep it safe from mortals who would seek to destroy it, or from demons who would simply consume it. Often found as the servants of evil Dragons or other powerful entities, a few Mortals have come face to face with a Shadow Demon near death, and been granted a boon; the Demon's eternal servitude. 

Once bound in this way, the Shadow Demon remains loyal to its new master, but it's desire to return to the Abyssal plane and reform in its to primary form remains, and those who form a pact with these creatures often find themselves pulled towards that tormented landscape of chaos and destruction.

Far more rare, but still possible, is for such a binding ritual to occur before the creature would be destroyed. When a powerful demon is near death and realizes that it will be trapped in the Material Plane, it may sometimes take up a pact with a mortal; this binds the demon to the Mortal's soul before it becomes a Shadow Demon, granting new, unique powers. The exact form the demon takes is determined by the player upon choosing which type of demon you have made a pact with, though its stats remain the same regardless of appearance. You may take a pact with a Shadow Demon freely; if you make a pact with any other type of demon, you must work closely with your DM for approval as such a relationship can have great consequences for both the character, the Material Plane, and the Abyssal Plane.

Summon Pact Demon

When you bind a demon to your service, you choose which form the demon takes. The most common is a Shadow Demon, though other demons have on very rare occasion been placed in situations that force them to either make a pact with a member of the Material Plane, or perish forever. The consequences for both parties can mean safety, but carry dire consequences. 

For the Warlock, their soul is forever drawn towards the Abyss; bound to a demon gives them unnaturally long life, but the darkness beneath the world haunts them at every turn. For the demon, they may find the Warlock a safe haven, but are now bound to their new master's life; if the Warlock dies so does the demon. So long as the Warlock lives, the demon may continue to regenerate, but the death of their master spells their final doom.

Upon choosing this feature, pick between a Shadow Demon or a War Demon. These encompass the two forms that are most common, though even so, such a relationship is vanishingly rare, coming about through chance rather than design.

Shadow Demon

Once per short rest, you may summon your Shadow Demon within 30 ft. of you as an action, as long as the space is unoccupied by a creature other than yourself. When it appears, each creature within 10 feet of the spirit (other than you) must make a Charisma saving throw against your spell save DC. On a failure, they take 1d10 psychic damage and are frightened - both of you and your demon - until the end of your next turn. 

The demon is friendly to you in a general sense - it does not wish you any specific harm - and unfriendly towards your companions but not openly hostile. However, it will obey your commands provided those commands do not act against its ultimate goal; you are unlikely to be able to command your demon to permanently seal transport to the Abyssal plane, for example. It has no qualms about fighting other Demons; those who form a pact with a Mortal are looked upon as abhorrent and are marked for death.

See the demon's in-game statistics in the Shadow Demon stat block below, which uses your Proficiency Bonus (PB) in several places. 

Shadow demon

Medium fiend

Armor Class 14

Hit Points 5 + five times your warlock level

Speed 30 ft., fly 30 ft.

Skills Stealth +PB

Damage Immunities Cold, Poison

Damage Resistances Acid, Fire, Necrotic

Condition Immunities Exhaustion, Grappled, Paralyzed, Petrified, Poisoned, Prone, Restrained

Senses darkvision 120 ft., passive Perception 11

Languages Abyssal, Telepathy to its Master (120 ft.)

Challenge — Proficiency Bonus (PB) equals your bonus

Incorporeal Movement. The demon can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object or creature that isn't its master. When occupying its master's space, any creature attempting to strike it do so at disadvantage. This feature cannot function if its master cannot cast a shadow at least 1 foot in diameter.

Light Sensitivity. While in bright light and not occupying its master's space, the demon has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

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

Actions

Shadow Claws. Melee Weapon Attack: your spell attack modifier to hit, 10 ft. reach, one target you can see. Hit: 1d8 + PB psychic damage.

Cloak of Darkness. When the demon takes the Hide action, it can also hide one other creature of your choice within 5 feet of it, provided that creature is in dim light or darker. Both creatures use the Shadow Demon's stealth roll for this feature. 

In combat, the demon shares your initiative count, but it takes its turn immediately after yours. The only action it takes on its turn is the Dodge action, unless you take a bonus action on your turn to command it to take another action. That action can be one in its stat block or some other action. If you are incapacitated, the demon can take any action of its choice, not just Dodge. Even the most brutal War Demon will act in the best way to save it's master.

The demon manifests for 1 hour, until it is reduced to 0 hit points, until you use this feature to summon the demon again, or until you die. If your demon is killed when you are dead, it is permanently destroyed and cannot be re-summoned, except by a wish spell. If killed while you are alive, your Demon regenerates after 1d6 minutes. 

When not summoned, your Demon still exists inside of you. Most often they will give a trinket to their master or change their body in some way, to allow communication while not summoned. This often takes the form of jewelry, perhaps a gem implanted in the creature, or sometimes even a second mouth or pair of eyes that manifest on their master.

War Demon

Once per short rest, you may summon your Demon within 30 ft. of you as an action. This space may be occupied. When it appears, each creature within 10 feet of the demon (other than you) must make a Dexterity saving throw against your spell save DC. On a failure, they take 1d10 fire damage as flames erupt from your demon's arrival. If the space was occupied and the creature occupying it failed its Dexterity save, it takes 1d6 damage and is knocked prone. 

The demon is friendly to you in a general sense - it does not wish you any specific harm - and unfriendly towards your companions but not openly hostile. However, it will obey your commands provided those commands do not act against its ultimate goal; you are unlikely to be able to command your demon to permanently seal transport to the Abyssal plane, for example. It has no qualms about fighting other Demons; those who form a pact with a Mortal are looked upon as abhorrent and are marked for death.

See the demon's in-game statistics in the War Demon stat block below, which uses your Proficiency Bonus (PB) in several places. 

War DEMON

Medium fiend

Armor Class 15 (steel breastplate)

Hit Points 6 + six times your warlock level

Speed 40 ft., fly 20 ft.

Skills Stealth +PB

Damage Immunities Cold, Poison

Damage Resistances Acid, Fire, Necrotic

Condition Immunities Exhaustion, Poisoned

Senses darkvision 120 ft., passive Perception 12

Languages Abyssal, Telepathy to its Master (120 ft.)

Challenge — Proficiency Bonus (PB) equals your bonus

War Beast. The Demon's attacks count as magical for the purposes of overcoming resistances.

 

Actions

Longsword. Melee Weapon Attack: your spell attack modifier to hit, 5 ft. reach, one target you can see. Hit: 1d10 + PB slashing damage.

Hellfire Whip. Melee Weapon attack: your spell attack modifier to hit, 15 ft. reach, one target you can see. Hit: 1d6 + PB fire damage.

In combat, the demon shares your initiative count, but it takes its turn immediately after yours. The only action it takes on its turn is the Dodge action, unless you take a bonus action on your turn to command it to take another action. That action can be one in its stat block or some other action. If you are incapacitated, the demon can take any action of its choice, not just Dodge. Even the most brutal War Demon will act in the best way to save it's master.

The demon manifests for 1 hour, until it is reduced to 0 hit points, until you use this feature to summon the demon again, or until you die. If your demon is killed when you are dead, it is permanently destroyed and cannot be re-summoned, except by a wish spell. If killed while you are alive, your Demon regenerates after 1d6 minutes. 

When not summoned, your Demon still exists inside of you. Most often they will give a trinket to their master or change their body in some way, to allow communication while not summoned. This often takes the form of jewelry, perhaps a gem implanted in the creature, or sometimes even a second mouth or pair of eyes that manifest on their master.

Chains of Ruin

Once per round, when you use an action to cast a Warlock spell of 1st level or higher, your demon can use its reaction to make an attack immediately after your action. If the attack hits, it deals bonus force damage equal to the level of spell cast. 

In addition, your demon can function as the point of origin for any Warlock spells you cast. 

Heart of Darkness

The pact between you and your demon grows ever stronger. You begin to manifest demonic features of your choosing; small horns, the first growth of leathery wings, a smell of sulfur, strange eyes, or a tail. As a bonus action, you can reveal some aspect of your Demon; either speaking with its voice, summoning it, or some other revelation. Doing so grants you advantage on Charisma (Intimidation) checks but disadvantage on Charisma (Persuasion) checks. If your target is a fiend, you only gain advantage if the CR of the target fiend is half your Warlock level (rounded up) or lower.

In addition, your pact allows you and your demon to enhance each other's abilities in combat. 

Shadow Demon

Once per turn, when you deal damage to a creature while you are obscured by shadow and your Shadow Demon is summoned, you deal 1d8 psychic damage to that creature as shadows lash out to harm it. While you are obscured by shadow, you have a fly speed equal to your movement speed, though your movement cannot pass through more than 5 ft. of bright light.

In addition, once per short rest, you may use your action to create a cloak of darkness extending 5ft from you in all directions. This cloak moves with you at all times, and you may occupy any space within the darkness. While inside, you have three-quarters cover from any creature that cannot see through magical darkness. Blindsight and similar senses treat you as having half cover, though True Sight pierces this feature entirely. Once you use this feature you are incapable of using it until you finish a long rest.

 

War Demon

Your War Demon becomes a Large creature, and you may ride it provided its form would allow such. Whenever your demon uses the attack action on its turn, it can make a second attack as part of the same action, using either its main weapon or its flame whip. You may also expend a spellslot to empower you and your demon; you and your demon heal for 1d4 hitpoints per level of spell slot expended (to a maximum of 5) and your demon gains a bonus to attack and damage equal to the level of spell expended (maximum of 5) until the start of your next turn. 

In addition, whenever you have summoned your War Demon, it gains a fire aura in a 5 ft. radius, dealing your Charisma modifier in fire damage to all creatures other than yourself that enter the aura or start their turn in the aura. You may activate and dismiss this aura as a free action. It can be active for a number of minutes equal to your Warlock level, after which it can not be used until you finish a long rest.

Unbound Abyss

Your connection to your demon has grown strong enough that you are able to maintain its form outside your body constantly. Your demon can remain manifested indefinitely. You may telepathically communicate with your demon as long as it is on the same plane as you. If it is on a different plane, you know which plane it is on, though you don't know its exact location. As your powers have grown, so has your reputation; lower demons may look to you for protection, or as a master to serve. Powerful demons may begin to see you as an enemy, while devils and other forces of order see you as a threat.

Once per day, you may channel the full power of the Abyss in to yourself. You gain a number of temporary hitpoints equal to twice your Warlock level, and your demon gains half that amount. You manifest an aura of shadowflame, that deals 1d6 fire and 1d6 psychic damage to any creature within 10 ft. of you. You gain a fly speed equal to your movement speed. You can maintain this form for 10 minutes or until you are incapacitated; while you maintain this form, you may cast a word of doom upon a single target, granting your demon advantage on all attacks against the target. Each attack rends their soul; whenever your demon strikes a doomed target, it takes your shadowflame aura damage as bonus damage.