Base Class: Rogue
As you walked the dark path of rogues, you discovered your true vocation lies in the shadows. Maybe you are a descendant of a creature from the realms of shadows, or maybe you've learned the ways of the shadowblood from a master. Regardless, the blood that runs in your veins bears unusual abilities. Your powerful "shadowblood" grants you talents that many cannot comprehend. You can imbue your weapons with shadow and the poisonous, life-giving ichor of yours. You have limited access to a plane of shadow, to which you can travel and reappear somewhere else in the material plane afterwards.
You are a master of shadows; you stalk your enemies in the dark and hit them hard before they even have a chance to realise what is going on.
Shadow Lurker
When you choose this archetype at 3rd level, you gain the ability to lurk in the shadows. You have advantage on your Dexterity (Stealth) checks while you are in a lightly or heavily obscured area.
Also, you gain darkvision out to a range of 60 feet. If you already have darkvision, its range increases by 30 feet.
Bloody Steps
Also starting at 3rd level, you can take a bonus action to deal blood damage to yourself and teleport to an unoccupied space that you can see. For each point of blood damage you deal to yourself, the range of the teleport increases by 5 feet, up to a total of 30 feet.
If you teleport within 5 feet of a hostile creature using this feature, the you gain advantage on the first attack roll you make against them before the start of your next turn.
You can use this feature a number of times equal to your proficiency bonus. You regain all expended uses when you finish a long rest.
Blade of the Shadowblood
When you reach 9th level, you can take a bonus action to imbue a weapon you are holding with shadows until the end of your next turn. When you do, the weapon turns pitch black, and you have advantage on attacks made with this weapon. Your first successful hit with this weapon deals an additional 2d6 necrotic damage, which transforms the weapon into one made of shadowy blood for 1 minute. For this duration, once on each of your turns you can choose to deal an extra 2d8 blood damage on a hit.
The extra damage increases when you reach certain levels in this class; 3d6 / 3d8 at 13th level, and 4d6 / 4d8 at 17th level.
You can use this feature a number of times equal to your proficiency bonus. You regain all expended uses when you finish a long rest
Master of Shadows
Starting at 13th level, when you are using the Bloody Steps feature, the range of the teleport increases by 10 feet instead of 5 feet for each point of blood damage, and its new maximum distance is 60 feet.
If the unoccupied space you have traveled to is a lightly or heavily obscured area, you may choose to become invisible as a reaction right after you teleport. This invisibility lasts for 1 minute, or until you attack, cast a spell, or interact with an item.
Keen Edges
Starting at 17th level, your weapon attacks made with the Blade of the Shadowblood feature score a critical hit on a roll of 19 or 20.