Order of the shadows

Many blood hunters describe themselves as "protecting the realms from the shadows" however none are as adept at it as the order of shadows. While originally tied to the shadowfel and shadar kai they have since spread to the material plane where they have gained grudging acceptance from the other older blood hunter orders and solidified their reputation as a fearsome force. Dedicated to hunting evil in the cover of darkness, they are regarded with respect but some degree of suspicion by the other orders and their power makes members of this order prime targets should they turn evil due to their ability to wreak havoc in darkness and escape.

Rite of the shade

When you join this order at 3rd level you have survived the Rite of the shade, you gain the following benefits:

you gain darkvision to 120 feet or increase existing darkvision by the same amount.

You can blend shadow magic with your blood maledicts to create additional effects, you can expend a use of your blood maledict feature to cast darkness on an area rather than an object and you can see through it, to cast shadow blade, or to turn invisible for as long as you remain within an area of darkness or dim light and move no more than half your speed per turn. Attacking or moving more than half your speed will make you visible until the start of your next turn and leaving the dim light or darkness will end this effect. It can also be ended by dispel magic.

You learn the Rite of the Shade as part of your Crimson Rite feature. When you activate the Rite of the Shade, the extra damage dealt by your rite is necrotic damage. Additionally, while that rite is active on your weapon, you gain the following benefits:

• Your weapon reduces light within 5 feet to dim.
• You have resistance to radiant damage.
• you have advantage on attack rolls made in darkness.

You can use this on shadow blade but because they are both concentration you can't have shadow blade and darkness active at once, so unless you are in natural darkness you won't be able to make use of the potential double advantage. Pick the better option depending on the conditions.

Though technically situational the invisibility doesn't require concentration and lasts until you choose to end it or until you lose the dim light or darkness, so it can last a long time.

*shadow blade is not free contant so I couldn't share this subclass with it in the class as a granted spell, I tried to add an ability that replicated it instead.

Enhanced blood maledict

Starting at 3rd level,you can use shadow magic to enhance your hemocraft abilities, gaining additional uses of your blood curses equal to half your proficiency bonus rounded down.

Terror of the night.

Starting at 7th level your power over shadows and darkness can confuse and terrify your foes. When you activate your rite of the shade you can choose to force any non ally that sees you do it to make an intelligence save (save dc = 8 + your proficiency bonus + your hemocraft modifier) or be frightened of you for a number of rounds equal to one roll of your hemocraft die. 

Whether they succeed or fail the save every creature that makes it is immune to this for the next 24 hours.

Hemocraft modifier intelligence.

Your hemocraft modifier is intelligence.

Hemocraft modifier wisdom.

Your hemocraft modifier is wisdom

Shadow Step

Upon reaching 11th level, You can magically step into and between shadows, as a bonus action you can teleport from any area of darkness you are in to any other area of darkness you can see within 120 feet. You can only use magic darkness if you can see through it and your own doesn't count due to its hemocraft based nature interefering with the teleport. Every time you use this you have to make an intelligence or wisdom save, this save increases by one every time you teleport , starts at 10 and decreases by one for every minute that passes since you last used this bonus action, however it drops straight from 10 to 0. If you fail the save you fail the teleport and you land anywhere within 5 feet of the target, this can include on top of things but you cannot end up inside an object, if you fail by more than 5 you take force damage equal to the amount you failed by multiplied by 5 and cannot teleport again until you complete a long rest.

Blood Curse of darkness.

At 15th level, you hone your hemocraft and shadow magic to learn the blood curse of darkness, the most horrifically evil blood curse known to mortals. So awful is this curse that many blood hunters refuse to wield it and its use is frowned upon except in life or death situations. However the wielder will pay a heavy price for its power and it can only be used once a day so it is usually saved for emergencies. It is also known to be used by evil blood hunters as a torture method, people held captive by any evil blood hunter known to be able to wield it are known to kill themselves just to avoid being subjected to it, such is it's reputation.

Blood curse of darkness.

This uniquely horrific curse uses an action and infects a creatures blood with the necrotic power of your shadows, turning it as black as midnight. The creature takes 4d12 necrotic damage every turn for half a minute and if they die to this damage their soul comes back as a shade that obeys you, this shade lasts until your next long or short rest. 

Amplify. If amplified this curse is even more horrific, the duration is doubled, and the targets blood turns thick and soupy, they experience extreme agony, they gain disadvantage on strength and dex checks and their movement speed drops to 1/4.

This curse, while horrifyingly effective, exacts a heavy cost for its effectiveness and it is not uncommon for novices to kill themselves attempting to learn it. Using this curse requires 2 uses of your blood maledict feature, it can only be used once per long rest, it requires concentration as a spell would and when you amplify it you take 4 times the normal amount of damage due to the energy needed to sustain it.

Shadow incarnate

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Upon reaching 18th level, you learn to use your shadow and blood magic to enhance yourself. As an action you can take on a form of pure shadow and darkness and radiate an aura of necrotic shadows that surrounds you and harms enemies. This transformation lasts for 1 minute.

In this form, you have resistance to bludgeoning, piercing, slashing, fire and cold damage, immunity to necrotic damage and vulnerability to radiant damage. Additionally any creature that gets within 10 feet of you, including allies, takes 2d8 necrotic damage for every turn it spends there This area is also dark though like your darkness spell you cannot use this with shadow step.

You can use this once per long rest for free and can reactivate it by expending 2 uses of your blood maledict feature AND taking necrotic damage equal to 2 rolls of your hemocraft die.

You still take damage from using crimson rite while in this form, specific beats general and crimson rite specifies that you cannot reduce the damage in any way.