Void Runner

Void Runners are usually the result of some unplanned or unexplainable magical experiment gone horribly wrong. To date, no one has identified a method to intentionally create one. Hopefully that remains the case as these endlessly essence-hungry rogues, assassins, and thieves can be terrifying to behold in action. They are extremely difficult to catch and all but impossible to detain due to their inexplicable connection to the darkest portions of the Plane of Shadow. Their ability to slip in and out of the Shadowfell at will is what makes them so difficult to hold. Their natural resistances to Necrotic or Negative energies and poisons all combine to create one of the most terrifying assassins.   

Dark Gift

3rd Level Feature 

You gain proficiency with the Stealth skill.

You gain resistance to necrotic energy and poisons.

Hunger of the Void

Being touched by the Void has cursed you with a terrible ever present hunger for energy, however you gain resistance to necrotic energy and poisons along with a special affinity in using them, and are particularly difficult to spot. If the Void Runner does not feed their hunger once every 72 hours, the hunger will begin to consume the Void Runners own vitality, consuming 1 HD for each day the hunger is not sated. The Void Runner is also unable to regain these consumed HD until the hunger has been sated. After all HD are consumed, each day after will begin inflicting 1 level of exhaustion as they are no longer able to sleep due to the tearing hunger of the void. These exhaustion levels are removed once the Void Runner has used their Drain Life ability and completed a long rest.

Draining Touch

This magical touch attack that deals 1d8 necrotic damage + your Wisdom modifier and restores the same number of hit points to the Void Runner. After using by this attack, the Void's hunger becomes sated. This ability can be used a number of times equal to your wisdom modifier and its uses refresh on a long rest. The damage increases at level 10 to 1d10 necrotic damage, at 17th it increases to 2d10.

Flicker

3rd Level Feature

Your connection to the Shadowfell allows you to flicker in and out of reality and briefly travel quickly on the field of battle. You may use your Cunning Action to Teleport up to half your movement speed in any direction. This movement type is separate from your regular movement speed. Using this ability does not trigger an attack of opportunity. The space you appear in must be visible to you and cannot be occupied by any obstacles. At 13t​h​ level, you can teleport up to your full movement speed in any direction when you use this ability. This ability is considered extra-dimensional travel and can be blocked by spells and items that prevent that or similar effects. You may use this a number of times equal to your proficiency bonus per short rest.

Void Mark

3rd Level Feature

You have proficiency with the Poisoners Kit.

You can place a purple Void Mark on any solid surface. These marks cannot be placed upon creatures or people. By default the last mark placed is the one that is considered Activated unless stated otherwise by the player. You can place an un-activated mark if you wish, provided you share that intent with your Gamemaster. An Un-activated mark can be removed with soap and water. An activated mark can only be removed by a Dispel Magic until it naturally dissipates. The mark lasts an hour per level in this class and only one mark may be Activated at a time. It takes an action to Activate a different mark and Marks can be Activated regardless of distance provided it is on the same plane of existence. You can use your action to teleport back to your mark as long as you are on the same plane of existence. The mark is consumed by your teleportation. You can place as many Void Marks as your Wisdom Modifier and regain uses after a Long Rest.

Shadow Walk

9th Level Feature

When in an area of dim light or darkness, you can use your action to become a shadow. While transformed, you have advantage on stealth checks, do not make any noise when moving, and can squeeze through an opening as small as 1 inch. You return to normal if you attack or take any action that affects a creature other than yourself, or if you end your turn outside of an area of dim light or darkness. If you revert form in a space you can’t normally fit, you are shunted to the nearest available space, and take 1d10 force damage.

Umbral Veil

13th Level Feature

Your experience with the Shadowfell has taught you how to steal the shadows of others and use them to defend yourself. When you kill a creature with your sneak attack, your Void energies rip and tear the creatures shadow from their body which can be used to protect yourself. When a creature is killed with your Sneak Arrack, you gain Temporary HP equal to their HD or CR times your Wisdom modifier plus your level in this class. You can use this feature a number of times equal to your proficiency modifier. If a creature who's shadow you have used in this way is later returned to life, they do so without a shadow and they are aware of what you used it for. 

Shadow Assault

17th Level Feature

Your mastery of the void has gifted you with the ability to become a terrifyingly fast specter, striking down multiple opponents in the blink of an eye. As an action, you can make one sneak attack and then immediately teleport up to your movement to another target and perform another sneak attack if your attack succeeds. You may do this up to three times per Shadow Assault. You may only strike each target once per round with a successful Shadow Assault activation. If your first strike misses, Shadow Assault does not activate and ends early if you miss an attack on the next target. You may activate this one time per proficiency bonus and your uses reset on a long rest.