Demon Blade

You yourself are the weapon, but incredibly cursed.
(There may only be one Demon Blade per campaign.)

Triple Edged Sword

You gain the legendary Demon Blade, Masamune; however you are incredibly cursed. Your blood is now black. Your blood is your weapon and your weapon is your blood. You may never be separated, even after death. This weapon can be summoned from your body, creating an open wound, and returned to the form of your blood at will. All wounds created via black blood are healed once returned to your body. The sword is incredibly cursed. Anyone killed by this blade has their soul absorbed by it to increase its power. You constantly hear the screams of anguish and demonic whispers that come from the sword and your blood. You are never mentally stable. You gain the following effects from the sword and the madness you've manifested from it:

You gain the "Haunted One" background.
Your black blood is a weapon harder than Adamantine, granting a +5 bonus to AC, a +2 bonus to Constitution, and a +2 bonus to Strength.
You may harden and loosen your blood at will. You are in turn immune to the Bleeding status effect.
You have trouble getting good sleep. You are only able to regenerate abilities that require a long rest once every 3 long rests.
You cannot drink potions.
You may only learn spells through feats.
You cannot use shields.
The voices are loud and evil. You are almost always inclined to kill upon winning a battle, especially when they attacked first.
You must attack at least once per turn, if possible, when in combat (unless retreating).
You feel compelled to repeat a specific activity over and over, such as washing hands, touching things, praying, or counting coins.
You are immune to all other madness effects, regardless of their origin.
It's hard to talk to people with all of the voices in your head. You gain a -2 to Charisma.
You don't eat much and are therefore thinner than you should be, but it's okay your blood is black. You gain a +1 bonus to Dexterity and proficiency in Stealth.
You have an incredibly difficult time focusing. You cannot concentrate on spells or anything else. Additionally, you gain disadvantage on Wisdom, Intelligence, and Charisma skill checks and saving throws.
Your saving throws are now Dexterity and Constitution.
(There may only be one Demon Blade per campaign.)

Secondhand Mastery

The souls your blade devours grant you their abilities and skills. You may acquire 1 feat of your choice.

Vorpal Hemorrhage

Did you know my blood is black?

Your blood is a weapon that you can control at will. If you are hit by a melee attack that causes you to take piercing or slashing damage, needles of black blood quickly erupt from the wound. The attacker must make a DEX saving throw with a DC of 15. On fail, they take 1d8 piercing damage. This die increases by one every 3 levels. Additionally, if it misses, your blood is left on the battlefield. On your turn, you may use it to make an attack on any creature within 30ft of you (unless they're behind cover) as a bonus action, causing 2d6 piercing damage.

Sentient Blood

Your black blood is sentient, moving your body for you when you need it to. You may use your bonus action to make an extra attack once per turn. Additionally, you gain an extra bonus action, a speed increase of 10ft, and your rate of exhaustion is halved.

Mephistophelian Metamorphosis

Your black blood is incredibly potent. You may summon very large, demonic wings formed of your black blood that burst through your back, granting a flight speed of 70 ft.

Merciless Onslaught

Four encounters per long rest, you may summon a second Demon Blade, Masamune, so long as your other hand is free, for the duration of the battle. During this time you gain the Two-Weapon Fighting style and an extra bonus action. If you already have the Two-Weapon Fighting style, you gain the Dual Wielder feat for the duration instead. Alternatively, you my summon a much larger, heavier version of the demon blade, Masamune for the duration of the battle. During this time the sword is granted the Two Handed weapon property, an extra 5ft of reach, an additional 2d8 of Bludgeoning damage, and the Great Weapon Fighter style. If you already have the Great Weapon Fighter style, you gain the Crusher feat but without the stat bonus.