Blood Weavers

A wizard who practices blood magic is one who has found the unshakeable connection of all life to the weave and uses the inherent arcane presence to amplify their own spells capabilities. They often sacrifice portions of their own vitality in such a process, but to blood mages the ends almost certainly justify the means. Some  blood mages dwell deep within cult compounds using their magic to appease evil deities from beyond the voids, others use their closer connection with the weave as a means of pushing themselves to edges of discovery and finding the true limits of arcane power. The one thing they all have in common? You never want to be across from an angry one.

Sanguimancy

At 2nd level, you have experienced a greater understanding of blood and how to manipulate it for better or worse. As an action you can force any creature you touch to make a Constitution saving throw against your spell save DC. On a failure they immediately spend and roll two of their Hit Dice and take that much necrotic damage. Alternatively, you can choose to have them regain that many Hit Points. You can use the ability a number of times equal to your Intelligence Modifier (min. 1) and regain all expended uses on a long rest.

Blood Rites

Starting at 2nd level, your ability to weave your lifeforce into the spells you cast helps offset the need for material components. You can use your own blood as a spellcasting focus even as it flows through your veins. In cases where the material components have an associated GP cost you must have at 1 current Hit Point for every 5 gold pieces of required materials. If the materials are consumed by the spell you take the necrotic damage equal to the material cost divided by 5 (rounded down). You still follow all other requirements for somatic and verbal components for spells.

Tough Blood

 At 6th level, you can bind your spells in blood to maintain them in circumstances which you normally would not be able to. As a reaction whenever you are forced to make a saving throw, you can choose to spend one hit die and add it to the result of your roll. Whenever you spend a hit die in this way you take damage equal to the amount rolled.

Arcane Blood

At 10th Level, your blood has become fully accustomed to the abnormal strain your magic puts on it. You have resistance to necrotic damage. Whenever you roll Hit Dice to regain health or increase your Hit Point Maximum, you roll each die twice and take the greater of the two rolls.

In addition, whenever you deal damage to a creature with a spell cast with your Blood Rites feature you regain a number of hit points equal to your Constitution modifier (Min. 0).

Rend Vitality

At 14th level, you add the Harm spell to your spellbook and can cast it once without expending a spell slot. When you cast that spell using this feature, you can regain 1 Wizard Hit Die for every 6 damage this spell deals. You can not cast this spell again in this way until you complete a long rest.