Blood Magus

Being a Blood Magus, you are not like mages of other traditions. Your past has darkness and the cold of death. It might have only been a fleeting moment, but your heart stopped and at least for an instant you knew death. Then there was the sharp pain as you took that first breath, your heart surged with agony, and the first sound you could remember hearing upon returning to life was the pulse of life-giving blood through your veins. This flow of blood coursing through your body was sweet music: the sound of life. You could feel it reenergizing every particle of your form, flushing death away and leaving life in its place. It was thick and warm, and you greedily embraced it.

Seeking ancient and forbidden lost knowledge you have delved into lost blood rites, sacrificial rituals, and a greater understanding of the inherent magic found within living blood. Yours is the way of Hemoturgy, a tradition bathed in blood.

Adaptation:

A twist on the blood magus as presented here would be to tie the class to some deity or entity. Whenever the blood magus works his blood magic, he also gives blood sacrifice to the deity or entity so named, and it is through this bloody patron that the blood magus powers his magic.

Blood Savant

Beginning when you select this tradition at 2nd level, you can substitute a drop of your own blood for a spell's material components, if any, and in so doing increase the spell's power. The pinprick or minor knife cut to draw the requisite blood is a free action that deals 1 point of damage to yourself, but raises the spell's caster level by 1. Slashing and piercing resistance or immunity, if the character has any, doesn't apply to this damage. If a spell has a costly material component (greater than 10 gp), the component must still be provided. If a spell has no material component, a blood magus can still use this ability to enhance a spell if he desires.

Durable Casting

At 2nd level, you gain the knack for being able to concentrate on casting spells and maintaining them despite taking damage while doing so. For the purpose of making a Constitution check to concentrate on, cast, or direct a spell when you might be distracted by damage, you may subtract your level from any hit point damage dealt to you by an attack that strikes you during the action (or whenever you are subject to a source of continuous damage, such as Melf's acid arrow). You still take all the damage dealt to you, but the damage is less likely to affect your ability to cast, concentrate on, or direct spells successfully. In addition you gain advantage on all Constitution checks made to maintain concentration on spells or maintaining them when you might be distracted by damage.

Because of this ability, damage a blood magus takes from using his blood savant and bloodseeking spell special abilities never requires him to make a Concentration check to finish the spell he is casting.

Stanch

At 2nd level, your command over your own life's blood makes you difficult to defeat. When damage reduces you to 0 hit points, you can make a Intellegence saving throw (DC 5 + the damage taken - your level in this class). On a success, you instead drop to 1 hit point. You can’t use this feature if you are reduced to 0 hit points by a critical hit.

After the saving throw succeeds, you can’t use this feature again until you finish a short or long rest.

Scarification

At 2nd level,  you can inscribe spells on your own skin for later use. This process involves deeply scratching the skin (which deals no damage but often leaves scars). The scratches remain fresh until the inscribed spell is cast, at which time the wound heals normally.

Effectively, you may scribe one spell you are able to cast as if onto a scroll using an alternative medium, and you may do so no more than once per long rest.

The amount of time required to do this is 1/24th the normal required time and the cost is 1/2 the normal cost related to the level of the spell the character wants to scribe, as shown in the Spell Scroll Costs table found in XGtE.

Blood Draught

Starting at 6th level, you have learned how to store spells of up to 3rd level in your own blood. Effectively, you gain the ability to brew minor potions using an alternative medium. 1st level spell effects take 1 hour to "brew" and cost 12 gp in raw materials which must be ingested. 2nd level spell effects take 7 hours to "brew" and cost 50 gp in raw materials which must be ingested, whereas 3rd level spell effects take 21 hours to "brew" and cost 500 gp in raw materials which must be ingested.

Once "brewed," a blood draught remains in circulation within a your body. The maximum number of draughts you can store at one time is equal to your level + your Constitution score, but if you die, they are all immediately ruined-even if you are subsequently returned to life. Blood draughts are never accidentally lost through major blood loss or by a blood-draining attack.
To consume a draught, you pricks your skin as a reaction, automatically bringing forth the desired effect. Another individual can partake of a blood draught (if he or she has a strong stomach) by drinking 1 ounce of the blood magus's blood as a an action. The blood magus must have an open wound to share the effects of a blood draught with another creature; if he lacks one, the creature can inflict a wound that deals 1d4 points of damage to the blood magus as part of the action to consume the draught. Slashing and piercing resistance or immunity, if the character has any, doesn't apply to this damage. A blood magus cannot store his blood in a container to share at a later rime. The blood draught must be drawn fresh from his body, or it loses potency within 1 round.

Bloodseeking Spell

Beginning at 6th level, through blood rite you can imbue your spells with the ability to draw blood from your targets. To use this ability, you must inflict a wound on yourself; this is a free action that deals 1d6 points of damage to the you and becomes a normal part of casting the spell. Slashing and piercing resistance or immunity, if the character has any, doesn't apply to this damage A bloodseeking spell deals an extra 1d6 points of damage per 2 spell levels to each target that takes damage from the spell. This extra damage applies only to spells that deal hit point damage, not to spells that deal ability damage, ability drain, or other kinds of damage. Constructs, elementals, oozes, plants, undead, and any creatures without blood or a similar substance within their bodies are immune to this effect.

Thicker Than Water

At 6th level and higher, your vital fluids are even more under your control. When you are injured, your blood withdraws from the wound, avoiding some damage that you would otherwise take.

This ability gives you resistance to bludgeoning damage.

Awaken Blood

Beginning at 10th level,  you can bestow momentary consciousness on an opponent's blood. If you hit a foe with a spell touch attack, the opponent's blood tries to get free of its confinement-all at once. The pressure disrupts the victim's tissues, dealing 12d10 points of necrotic damage. This ability is usable only once per long rest, but a you can try to use it again if your previous attempt failed. The effect is instantaneous.

Constructs, elementals, oozes, plants, undead, and any creatures without blood or a similar substance within their bodies are immune to this effect.

Infusion

Upon reaching 10th level, you may prepare a special onetime distillation of your own blood. This distilled infusion takes 1 week to prepare and requires 5000 gp in other material components processed through alchemical devices.

After partaking of the infusion, you gain a 2 point increase to your Constitution score, and your maximum Constitution score is raised to 22.

Bloodwalk

Starting at 14th level, you can become perfectly attuned to the song of blood. You gain the supernatural ability to transport yourself great distances via the blood of living creatures. Once per short or long rest as an action you can seamlessly enter any living creature (except an elemental, ooze, plant, undead, or other creature without blood or a similar fluid) whose size equals or exceeds your own and pass any distance to another living creature on the same plane in a single round, regardless of the distance separating the two.

You merely designate a direction and distance ("a living creature twenty miles due west of here"), and the bloodwalk ability transports you to a destination creature as close as possible to the desired location. You can't specify a named individual as the endpoint unless you have previously obtained a sample of that creature's blood and have it preserved in a vial that you carry.

The entry and destination creatures need not be familiar to you. You cannot use yourself as an entry creature. If an intended entry creature is unwill­ing, you must make a successful spell touch attack to enter. (A missed touch attack does not use up the ability for that day.) When exiting a creature, You choose an adjacent square in which to appear. Entering and exiting a creature is painless unless you wish it to be otherwise (see below). In most cases, though, the destination creature finds being the endpoint of a magical portal surprising and quite unsettling. If you desire, you can attempt to make a bloody exit from the destination creature. If so, you burst forth explosively from the creature's body, dealing 14d10 points of damage unless the creature makes a Constitution save (DC 8 + Intelligence modifier + your proficiency bonus). When you make a bloody exit, you must succeed on a DC 15 Constitution save or be stunned for 1 round from the shock of your expulsion.