Blood of the Coven

Sometimes the ability to harness magical power is learned through study and practice, sometimes it's bestowed upon the user by even more powerful forces - in your case, the power was taken generations ago through the ritualistic sacrifice of a loved one. The mental and emotional wound caused by such a heinous act allowed dark witch magic to enter the body and fuse with the blood, creating a lasting connection that would be passed down from parent to child in an endless cycle that has left you feeling both gifted and cursed.

Just as the original ritual required sacrifice, so too does your ability to wield your innate magic. Your power surges after taking a life, and wanes the longer you go without killing, nearly depleting to nothing. In the heat of battle, your abilities increase as foes fall around you, but if you can't bring yourself to snuff out a living thing in cold blood when you're not fighting for your life, you might find that you have no power left the next time you are.

Witch's Sight & Understanding

You have darkvision that is so keen it allows you to see through even magical darkness. Additionally, you can both read and understand spoken Abyssal language, but you are unable to speak or write it yourself.

Sacrificial Surge

Starting at 1st level, any time a living thing that you've damaged while in initiative dies, you get 1 charge of Sacrificial Surge that can be consumed to add 1d4 to any non-saving throw roll; however, if at any point you have 0 charges of Sacrificial Surge, you cannot cast spells until you acquire at least 1. You may sacrifice a living thing out of initiative once per long rest for 1 charge of Sacrificial Surge.

The amount of added dice increases by 1 at levels 5, 10, and 15 (2d4 at 5, 3d4 at 10, and 4d4 at 15).

Blood Transfusion

Starting at 6th level, when you consume a charge of Sacrificial Surge to add to a damage roll, you can spend 1 sorcery point to return health equal to half of the damage dealt (rounded down) to yourself or a party member within 10 feet of the target you damaged.

Slow Pulse

At 14th level, you gain the ability to slow a target's heartbeat. If you have at least 1 charge of Sacrificial Surge, you can spend 1 sorcery point to use this ability as a bonus action. This breaks the target's concentration and moves them to the end of the initiative order for the next round.

Blood Explosion

Beginning at 18th level, you can boil the blood of a deceased target, causing it to explode from the corpse and then congeal on any enemy it touches. As an action, you can spend 4 sorcery points and consume 1 charge of Sacrificial Surge to cause the blood of a deceased target to explode in a 20-ft. radius. Each hostile creature caught in the explosion is incapacitated on their next turn. After that turn, they must succeed on a Wisdom saving throw or remain incapacitated for the next two rounds (three rounds total if they never succeed on the saving throw). A creature that succeeds on this saving throw is immune to this spell for 24 hours.