Haematurgy

A Wizard that has specialised in a certain branch of necromancy: Blood Control. These types of spellcasters wield their vital fluids as a weapon, both figuratively and literally.

I was inspired by Antonio Domico's Blood Thief rogue subclass to make a spellcaster that leans more into the using blood as a magical substance idea, originally slapped this all together in about 20 minutes or so in my notes app. Lemme know what you think :D

Empowered Vitality

From 2nd level, you gain a bonus to your hit points equal to half your intelligence modifier (rounded down, minimum of 0) each time you gain a level in the Wizard class.

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Blood Shaping

When you reach 2nd level, after you complete a long rest, you can expend 1 hit die to create a melee weapon from your blood. You are proficient with the chosen weapon and you use your intelligence modifier for attack and damage rolls made with it. The standard features of the chosen weapon apply to it. When not in use, the weapon can be stored as liquid blood in a suitable container, and you can use an action to summon it from the container. When you take a long rest, your blood weapon is reabsorbed into your body, requiring you to expend a hit die again after the long rest.

At 6th level, you can use your blood weapon as a spellcasting focus.

At 9th level, your blood weapon can take the form of a simple or martial ranged weapon. This weapon is compatible with the ammunition a standard weapon of its type uses, or you can sacrifice 5 hit points to create 1 blood ammunition. This ammunition can be used to trigger the Blood Thinner and Red Death features if they are available to you.

Alternatively, if you do not have a blood weapon currently active, you can spend a number of hit points equal to 10 - your proficiency bonus as a bonus action to create a set of tools. You are proficient with tools created this way. Created tools last 1 hour and cannot be stored but can be changed whilst still in use.

Blood Thinner

At 6th level, when you deal damage with your blood weapon to a creature with blood, you can make that creature make a constitution saving throw against your Wizard spellcasting DC. Upon a failure, the target begins to bleed profusely for 1 minute. Whilst bleeding, the creature has disadvantage on strength saving throws and ability checks, as well as Constitution saving throws, and it's movement speed is halved for the duration. You can use this feature a number of times equal to your intelligence modifier.

Bleeding Magic

At 10th level, you can cast a wizard spell that you have prepared without expending a spell slot by sacrificing a number of hit points equal to 4 times the spell level. Using this feature more than three times before completing a long rest afflicts you with a point of exhaustion for each use over the third.

Red Death

At 14th level, when you deal damage using your blood weapon, you can command your blood to enter the targets body and begin destroying it from the inside. Your blood weapon disappears, and the target is poisoned. It takes an amount of poison damage equal to your level in the Wizard class at the beginning of each of its turns until it reaches 0 hit points or you recall your weapon as a bonus action (this must be done from within 10ft of the afflicted creature).

This feature ignores immunity to the poisoned condition, as well as immunity or resistance to poison damage.