The Fiend-Blade

You have made your pact with a weapon of hatred a torment from the deepest parts of the Underworld. A sentient weapon with demonic energy has given you power in trade for your skill with a weapon. Be it a trapped minor deity or greater being within the weapon or a blade created of pure hatred, forged in the lowest planes of existence. Regardless, you may wield great hell-bound power, a harbinger of annihilation, at the cost of a little of your soul.

Expanded Spell List

The Fiend-Blade lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Fiend Expanded Spells

Spell Level	Spells
1st	burning hands, false life
2nd	flaming sphere, scorching ray
3rd	fear, fireball
4th	fire shield, wall of fire
5th	flame strike, immolation

A Catalyst

Your patron is trapped within a weapon, called the Catalyst, the being at your will, and you at it's. You have a weapon that contains the power of your patron. (It also looks cool!) The weapon may be any martial or simple weapon, and is now magical. If the magic in your weapon is disturbed, (ex. anti-magic fields) it reverts into it's original form, until undisturbed. The Catalyst (the weapon) does it's respective damage, along with 1d4 fire damage. The weapon can also talk to you, give you disadvantage, advantage, remove the fire bonus, or deal 1d4 slashing, fire, or necrotic to you, dependent on it's liking towards you.

Nether Branding

Starting at 1st level, you gain the ability to place a baleful curse on someone. As a bonus action, choose one creature you can see within 30 feet of you. The target is cursed for 1 minute. The curse ends early if the target dies, you die, or you are incapacitated. Until the curse ends, you gain the following benefits:

• You gain a bonus to damage rolls against the cursed target. The bonus equals your proficiency bonus.
• Any attack roll you make against the cursed target is a critical hit on a roll of 19 or 20 on the d20.
• If the cursed target dies, you regain hit points equal to your warlock level + your Charisma modifier (minimum of 1 hit point).

You can’t use this feature again until you finish a short or long rest.

(Yes, this is just a flavored Hexblade's Curse.)

Accursed Wielding

At 1st level, you acquire the training necessary to effectively arm yourself for battle. You gain proficiency with light and medium armor, and simple and martial weapons as well as your Catalyst.

The influence of your weapon also allows you to channel your fury through a particular weapon. Whenever you finish a long rest, you can touch one weapon that you are proficient with and that lacks the two-handed property. When you attack with that weapon, you can use your Charisma modifier, instead of Strength or Dexterity, for the attack and damage rolls. A creature hit with this weapon must succeed a DC 10 Wisdom saving throw or be frightened for the whole of combat. This benefit lasts until you finish a long rest. If you later gain the Pact of the Blade feature, this benefit extends to every pact weapon you conjure with that feature, no matter the weapon's type. 

If you wield any other weapon while not wielding your Catalyst, you attack with disadvantage. 

Leashed Beast

The wielder of the Catalyst is a sort of catalyst in itself, be it spiritually, or literally.

At 6th level, you may use an action to become a Barbed Devil, with all of it's stats, except you can vaguely speak your own language, forcing you to make a DC 15 Charisma saving throw and upon failure, you fail to speak, otherwise, speak in any language you choose. Your Wisdom, Charisma and Intelligence modifiers remain the same while transformed and you may cast any spells from your own, or the devils, spell list. The transformation ends when you use an action to dispel the transformation, knocked unconscious, or killed. If you die in your transformation, return to your original form, fail one death save and begin rolling death saves. When you transform, all items you have disappear, and reappear upon returning to your original form. Upon returning, your Catalyst will appear in your hand and you gain 4 levels of exhaustion. You can only do this once after a long rest.

Upon 8th level, you can instead become a Chain Devil, and upon 9th level, a Bone Devil.

 

Fodder Fuel

Your Catalyst isn't the only one who needs blood.

At 10th level, when you kill any creature, you gain health equal to your Warlock level and the creatures Challenge Rating. If the rating is below one, hold that number and continue adding numbers below one until it equals one, then, heal one health. (ex. You would need to kill 8 Giant Crabs to heal 1 health, due to it's 1/8 Challenge Rating. You could also kill 4 Giant Crabs and 1 Crocodile, and you can still heal one health. ) Any healing exceeding your maximum becomes temporary health, which is lost after 6 hours. (The 6 hour timer is reset upon gaining more health this way.) Gaining 10 temporary hit points can remove levels of exhaustion.

Demonic Mutualism

When a Catalyst, and it's wielder come to an agreement, they reach farther than any demon dare reach.

At 14th level, as an action, your Catalyst may wield itself, allowing you to do close-range combat at long range. Your Catalyst can reach 100 ft away from you. Your Catalyst counts as another creature. Your Catalyst is a Flying Sword, with the following exceptions.

• It does not have False Appearance
• It's maximum health is the same as your own maximum. (This does not mean you share health.)
• It's action changes to it's weapon type. Ex; A longbow Catalyst will attack as if it was a longbow, not as a longsword.
• It shares your Strength modifier.
• It's Charisma stat is 15.
• Once it dies, it returns to you, sheathed and unusable until after a short rest.

While wielding the Catalyst normally, you get advantage on checks using the Catalyst to attack. Your Catalyst also does an extra 1d8 damage. (ex. A Catalyst Warhammer does and extra 1d8 bludgeoning damage, not slashing or piercing.)