Blood Mage aka Hemomancy Origin

Your innate magic comes from studing your own bloodstream and blood flow. Perhaps you were a mad scientist, who decided to study and to better understand your own blood flow and it's magical propertise. Perhaps you were a wizard or a sorcerer, who was able to bend water at will and who during her decades long imprisonment decided to start to bend blood instead. Perhaps your peronality was quite emo and you became way too facinated with blood and self-harm.

As a sorcerer, whose magic originates from Hemomancy, you tend to harm yourself way too often and thus sorcerers like you tend to be short-lived. It is actually a miracle that you aren't already in a ditch somewhere bleeding to death. Sorcerers, whose magic originates from Hemomancy, tend to constantly walk the line of death and life, sanity and insanity. Because they risk with their lives on daily basis, sorcerers of Hemomancy tend to be more evil and more chaotic in nature.

NB! All abilities of this subclass only work on creatures, who have a bloodstream. Creatures, who don't have bloodstream, are ether Undead, Plants, Oozes, Elementals, Constructs or Living Constructs. DM may make exceptions and/or additions to that rule.

Fueled by Blood

You can inflict 1d6 slashing damage on yourself (unless you are without a bloodstream). Your maximum Hit Points are also temporarily reduced equal to the damage that you inflicted to yourself. This reduction lasts until your next long rest and this reduction can't be gotten rid of with spells. For every 2 points of damage, you gain 1 sorcery point. At 6th level, the damage die becomes d8, at 12th level, it is d10 and at 18th level, it is d12.

Additionally,  you gain ability to create 1st level spell slots with 2 Sorcery Points. Like every other sorcerer, starting at 2nd level, Sorcery Points become more useful to you.

Strength through Bloodshed

Every time you gain a level (inculding 6th level) as a Sorcerer, you can increase your maximum Hit Points equal to your Charisma modifier divided by 2 or you can increase your maximum hit points by 1 instead.

Additionally, constant self-harm has woken new powers in you. After you use Fueled by Blood ability, excess of blood oozes out of your veins and it creates a defensive crust on your skin. Until the start of your next turn you gain temporary resistance to slashing, piercing and bludgeoning damage from Nonmagical Weapons. You gain those resistances only when you don't wear any medium armor nor heavy armor.

Siphon Blood

You can siphon a stream of blood from a living creature at a distance.  As an action you may spend 5 sorcery points in order to target a living creature within 40ft that has a bloodstream. That creature must make a Constitution saving throw. When target fails it's save, blood oozes out through its skin and flows through the air to you, where it's absorbed through your skin. Target takes 3d6 necrotic damage, and you gain hit points equal to half the amount of necrotic damage dealt. Your Hit Point maximum is also increased equal to the amount of Hit Points that were gained with this ability. This temporary increase of maximum Hit Points lasts until your next long rest. 

Puppet of Blood

You can now make unwilling creatures into your obidient puppets. As an action you may spend 10 sorcery points in order to target a living creature within 30ft that has a bloodstream. Target makes a Constitution saving throw. Creature, who fails this save, becomes a puppet of yours. Puppet submits to your will. Puppeted creature takes only the actions you choose, and doesn’t do anything that you don’t allow it to do. You can always decide to make your puppet do simple and general course of actions (for example "Attack that creature", “Run over there”, or “Fetch that object"). You can use other actions and spells only when you have seen them being used by this creature or creatures like him. During this ability, you can also cause the creature to use a reaction, but this requires you to use your own reaction as well. During your control Puppet is suffering under immense pain and because of that target can't speak and target can't cast a spell that includes a verbal component. Duration of this ability is concentration (up to 1 hour) or until you end it. After 1 minute has passed from target's last try, target can make a new Constitution saving throw against the ability. If saving throw is succesful, your puppet breaks free.