Blood Mage

A Blood Mage uses a special type of magic called Sanguimancy to drain life from their enemies, adding it to themselves, and then using that life as a resource to make their spellcasting more potent. It is a dangerous balance to strike but for a Blood Mage, arcane power must be attained at any cost. Even your own life force. 

Constitution Casting

At 1st level, when you choose this sorcerous origin, your spellcasting ability for your sorcerer spells and abilities becomes Constitution instead of Charisma. Any feature that refers to your Charisma score or modifier instead refers to your Constitution score or modifier. 

Vital Mage

Beginning at level 1 when you gain this feature, and at every level thereafter, when you roll a number of Hit Points to determine your max HP for gaining a level in a class you add 2 to the amount rolled. In addition, when a spell would cause you to regain a number of lost Hit Points you regain extra hit points equal to your proficiency bonus. 

Cost of Power

Beginning at 6th level when you gain this feature, you may sacrifice your own vitality to increase your spellcasting potency. On your turn, you may use a bonus action to sacrifice a number of Hit Points to regain half as many Sorcery Points rounded down. When you use this feature you may only sacrifice a number of hit points equal to your sorcerer level. 

Perfected Body

By 14th level in this class your study of the body and use of vital force has made you resistant to those effects that would attack your biology. You become immune to disease and poison, as well as the poisoned condition. In addition, at the start of your turn you regain a number of Hit Points equal to your proficiency bonus, so long as you have no more than half of your Hit Points and at least 1 Hit Point. 

Grand Sanguimancer

At 18th level you have become so familiar with blood and Sanguimancy that you are able to transform into the living embodiment of it. You may use an action on your turn to transform yourself into a Blood Elemental. You gain resistance to bludgeoning, piercing, and slashing damage while in this form. You gain a fly speed and swim speed equal to twice your walking speed. And you halve the Hit Point cost of your Cost of Power feature. If you would regain a number of Hit Points in this form you regain twice as many instead. This transformation lasts for 1 hour and you may use this feature once per long rest.