Your magic is the magic within all living blood — and in your blood more than others. Blood magic comes easily to you, and you find that your blood is strong, and getting stronger the more you draw on its magical power. Most who have their blood continually tapped for magic begin to suffer illness and frailty, but your blood is different in some way. Perhaps your blood is growing stronger the way warriors train their muscles, or perhaps your blood carries a gift made for blood magic itself. Whatever it is, you feel your heartbeat grow stronger and louder with every growth in sanguine power.

Resilient Blood

At 1st level, your blood is infused with resilient life energy, allowing you to draw more from that wellspring. You have one bonus sorcerer hit die. You gain another bonus hit die when you reach 5th level, 11th level, 17th level, and 20th level in this class. These hit dice do not increase your hit point maximum.

Also, when you finish a short rest, you can choose to regain hit points equal to your Constitution modifier + half your sorcerer level (minimum 1). Once you do so, you can't do so again until you finish a long rest.

Finally, when you reach 6th level, you gain advantage on saving throws made to resist blood magic or disease.

Hematurgy

Starting at 1st level, you gain the ability to cast beyond your limits by sacrificing the vital life force inside your own blood. As a bonus action, you can spill your own blood and spend up to 5 of your remaining hit dice, but instead of healing you take 1d8 necrotic damage per hit die expended that ignores resistance and immunity. This damage doesn't cause saving throws to maintain concentration.

The next sorcerer spell you cast on this turn is also a Blood spell in addition to its other schools and does not require a spell slot if it would normally expend a spell slot of a level equal to or less than the number of hit dice you expended. If the casting time is 1 bonus action, you can cast the spell as part of using this feature.

As a bonus action on your turn, you can choose to expend any number of hit dice you have, regaining 1 expended sorcery point for each hit die you expend in exchange.

You can't use this feature to cast a spell at a level higher than you have spell slots for, and you can't expend more hit dice using this feature than half your sorcerer level (minimum 1) before finishing a long rest.

Bleed Magic

At 6th level, you gain the ability to cast spells when you are wounded, turning the blood spilt from your veins into magic as you bleed.

When you take slashing, bludgeoning, or piercing damage or damage from a Blood spell, if you have no more than half of your hit points remaining after taking damage, you can spend 2 sorcery points and use your reaction to cast one spell that would normally require an action or bonus action to cast. If you do so, you can't cast spells of 1st-level or higher on your next turn.

Crimson Power

Starting at 14th level, you learn how to make use of the blood your enemies have already spilled from you to strengthen your magic beyond its normal limits even as your blood magically shields you from harm. While you have no more half your hit points remaining, you gain a +1 bonus to AC and saving throws. If you roll damage for one of your sorcerer spells during this time, you add your proficiency bonus as bonus damage. A creature can only take this bonus damage once per turn.

Endless Blood

At 18th level, you become a magical font of blood. Your veins and arteries seem to never deplete of blood. At the start of each of your turns, you regain hit points equal to 3 + your Constitution modifier (minimum one hit point) if you have no more than half of your hit points left. You don't gain this benefit if you have 0 hit points, and this healing can't restore your hit points to more than half of your maximum hit points.

In addition, when you roll hit dice to regain hit points, you can roll twice and use the higher result, and when you roll damage for your Hematurgy feature, you can roll twice and use the lower result.

Finally, you regain all your missing hit dice when you finish a long rest, instead of only half of them.