It would be easy to assume that those druids who practice voodoo would have malicious intent, but those who are graced by their magical presence knows that it is a power of nature none the less. Practitioners realize the utilization of the life force of the land and its inhabitants is not always natural but respectful to life. Delving into this form of magic grants its wielder knowledge of the future, ability to manipulate the life force of other creatures, and access the world of shadow.

This subclass involves obtaining biological matter from friends, enemies, or suspicious peoples. The DM has final say on the procedure of obtaining this material. However, I would use these rules: A willing creature can give such materials, an unwilling and unknowing creature might need to make a perception check contested with the challengers sleight of hand skill, and material like blood or saliva can be recovered from blades, dining utensils, latrines, etc.. The difficulty of obtaining said materials should be dependent on the target. A note to players, while voodoo dolls are evocative when used offensively the defensive and supplemental benefits of this class can not be understated. It is more reliable and less tempermental to have voodoo dolls of fellow party members to cast healing, buffing, or transformative magics from afar.

It has been suggested that I create a doll tracker, but I can not seem to do it on D&D Beyond. If you would like one there is a link to a pdf document in the comments of this subclass.

Voodoo Doll

When choosing this Circle at 2nd level you can identify and tie the life force of a creature to an inanimate doll. During a short rest you can craft a doll that resembles a humanoid that you know. Once made, a piece of biological matter such as hair or blood must be applied to the doll in order to bind the creatures life force. Any spell cast on the doll affects the creature regardless of the distance between the caster and the creature as long as they are on the same plane of existence.

Any physical harm that comes to the doll does not affect the creature. You are able to have a number of dolls equal to your wisdom modifier, but can only craft one per short or long rest. Once you create an amount of dolls that exceed your limit the oldest active doll becomes inert. If a damaging spell cast on the doll does anything other than psychic damage, the doll is sundered, for the doll is still made of thread, straw, or other fragile materials.

Expanded Spell List

The following spells are added to the druid spell list: Detect Evil and Good, False Life, Inflict Wounds, Augury, Blindness/ Deafness, Gentle Repose, Ray of Enfeeblement, Animate Dead, Clairvoyance, Speak with Dead, Divination, Shadow of Moil, Contact Other Plane, Danse Macabre, Raise Dead, Create Undead, and Soul Cage.

Shadow Beast

There is more to the world than it seems, some things hide in the shadows and some things hiding are the shadow. When you wild shape your animal form is created of pure shadow. While in your wild shape form you have advantage on stealth checks, and all damage from your bestial form deals necrotic damage and is magical for the purposes of overcoming resistances.

Brace of Blood

At 10th level you are able to bolster your defense and gain a lucky edge against your opponents, at a price of course. 

As a bonus action you lacerate yourself so that your life energy can permeate. When you first activate this ability you take 1 damage. This effect lasts 10 minutes and while it's active you gain +1 AC for each voodoo doll that is in 100 foot range of the creature it is bonded too. Additionally, when rolling any damage die you can reroll 1 die for every point of health you sacrifice. You must keep the value of the rerolled die.

Shadow Magic

Your dealings with the supernatural have created a kindling between you and darkness. Whenever there are shadows around you can use an action to make them expand or shrink. While expanded dim light becomes darkness, and well lit to dim light in a 10 ft radius around you. While shrunk darkness becomes dim light , and dim light becomes well lit in a 10 ft radius around you. You can see perfectly in both magical and non-magical darkness. Additionally, you can use an action to attack any creature in darkness you created, when you do so all creatures of your choice in range must make a dexterity saving throw or take 10d4 necrotic damage on a fail or half as much on a success.