Order of stagnation

Using your rites poison the blood running through your enemies veins. After a successful hit with your weapon after activating a rite the target must make a constitution saving throw. (AC is 18) upon failing the target is poisoned and must do a saving throw the next turn if failed again poison affect continues until a save is successful. Poison damage is 6 d6 of poison.

Blood Stagnation

You begin to uncover forbidden magic that stagnates your targets blood in their veins.

Beginning at 3rd level, you learn a blood rite that uses your targets own blood as a poison damaging them from the inside. (They must make a saving throw for constitution AC 18). If failed the target is poisoned taking  3 d4 poison damage at 7th level, 11th level, 15th level, and 18th level gain 1 extra d4 adds up to total of 6 d4 in total

Additionally, when you sacrifice hit points you can gain an extra d4 (can be used as an action only once per turn unless your below 10 hit points.)

Venomous Saliva

Lick your blade coating it with your saliva which acts as poison. Adding 2 d4 poison damage to your attacks. (You can sacrifice 2 hit points to double the poison damage on an attack.)

Venomous Spit

You can cast poison spray on the target

Blood Curse of Blood Rot

Starting at 15th level, your blood curse can wrack a creature’s body with a terrible poison. You gain the Blood Curse of Blood Rot for your Blood Maledict feature. This does not count against your number of blood curses known.

Poison Blood Mastery

At level 18 your blood becomes a venom making you immune to poison and damaging enemies when they attack you.