Blood magic

Use your own HP as fuel for spells and other magical effects.

Blood fuel

You may sacrifice HP to cast spells instead of using a spell slot. The ammount of health is equal to (spell slot level)x10

i.e. a 3rd level spell slot will cost you 30 HP

Flow of blood

whenever you gain HP outside of your turn you can immediately spend the incoming hit points and cast a spell as a reaction.

i.e. Cleric Terra cast cure wounds on Blood wizard James, She is healing him for 24 HP. James uses his reaction to cast a 2nd level spell and only gain 4 HP.

Gorge on blood

Whenever you steal health from an unwilling opponent, you gain double the HP you normally would.

Fueled by blood mist

Whenever you kill an enemy you gain their remaining HP as Temp HP.

i.e. Blood mage James casts fireball on the Hill Giant. the giant has 34 HP. Jame's fireball does 45 damage. the remaining blood of the Hill Giant flows around James giving him 34 Temp HP.