Blood Mage

Necromancy has long been the most scrutinized and hated study a wizard could specialize in, but many do not remember the magics that necromancy evolved from. Blood magic is the primal form of necromancy utilizing the blood of both living and dead creatures to empower yourself, or to manipulate others into doing your bidding. The victims of a blood mage are helpless to watch as their bodies refuse their commands and instead follow the orders of some hidden puppeteer, or as a ally falls in battle and sacrifices themselves to empower a blood mage's next spell. Blood mages have mostly been hunted down and killed due to the believed innate evil nature that is beholden to such magic. This magic is nearly a forgotten school of wizardry and should be treated as such. Spells related to blood magic are not nearly as plentiful and readily available as other such spells, but a blood mage's power lies in the abilities they are gifted with.

Potent Blood

Starting at 2nd level, you may use your own blood in place of costly spell components that have a gold cost. Casting a spell in this way is taxing and hurts the wizard immensely. When using your blood to cast a spell, you take 1d10 x spell level in force damage as your body is wracked with the power of the spell you cast.

Constricted veins

Starting at 2nd level you learn to constrict and slow the blood flow of a creature. One creature within 30ft of you must make a Constitution saving throw against your spell save DC. On a failed save the target's speed is halved and their attacks are made at disadvantage. This effect lasts for 1 minute and you may use this feature a number of times equal to your constitution modifier (minimum of 1).

You regain all uses of this feature on a short or long rest.

Blood Strings

Starting at 6th level you know how to use the blood within a creature to control it. You may target a large or smaller creature. That creature makes a constitution save versus your spell save DC. On a failed save the target falls under your control for 1 hour. You may use your bonus action to control the target to take its actions as normal. The target may repeat its saving throw at the end of its next turn if it takes damage any time during a round. 

You may use this feature twice and regain the use of this feature on a long rest.

Worthy Sacrifice

Starting at 10th level you may now utilize the blood of fallen enemies or falling allies. You may use the blood from a corpse within 10ft of you to either empower, or overpower your next spell. If you use the blood of an enemy the spell becomes empowered. If you use the blood of an ally, the spell becomes overpowered.

When your spell is empowered, the damage, if any, increases by a number of dice equal to the spells level. Cantrips are considered 1st level for this case. If the spell has a saving throw, the target has disadvantage.

When your spell is overpowered, all of your damage dice is maximized. If the spell requires a save, the target automatically fails it. This feature overrides any auto saves that the creature might have.

In order to overpower a spell an ally must be currently be making death saving throws, and must sacrifice themselves to overpower the blood mage. When the ally does so they instantly die. When an ally who dies this way and an attempt to revive is made, they must make a constitution saving throw versus the blood mages spell save DC. On a failed save the ally does not revive.

You may use this ability equal to your constitution modifier (minimum of 1). You regain all uses of this feature when you take a long rest.

Hemostasis

Starting at 14th level, you learn to paralyze a target using blood as the component. The target must make a constitution saving throw against the wizards spell save DC. On a failed save the target is paralyzed for 10 minutes. You must maintain concentration on this effect as if it were a spell. For each minute the target is paralyzed they take 5d10 force damage (this may be either lethal or non-lethal). After every minute the target may repeat the saving throw. Once you use this feature, you may not use it again until you take a long rest.