Hunter-Killer

You are a living weapon. You have been afflicted by a twisted form of necrotic magic which enhanced your body's natural capabilities. From sprouting razor sharp claws, to being able to cloak yourself in a veil of magic, no creature can hide from you, and no spell can hide someone from your sight. Those who become Hunter-Killers usually live lives of being feared and rejected. Occasionally they will become feral, living in the wilds and hunting their prey like animals. Some are used as necessary evils by military and aristocrats to assassinate special targets. The mercenary business is also bound to have Hunter-Killers which make a living off their power. The scope of life which Hunter-Killers thrive in matches up to their adaptability and toughness. How you choose to use your powers is up to you. 

Dread Mutation

When you reach 3rd level, the vil magic in your blood erupts and changes your body. Your unarmored AC now equals 13 + your Dexterity modifier, and you gain resistance to necrotic damage. You can use your natural armor in place of your armored AC if the value gained from wearing armor would be lower. 

Natural Weapons

Also at 3rd level, you gain two natural weapons which get stronger as you level. You are considered proficient with both weapons. 

Claws. Your fingers sprout bony claws, allowing you to make unarmed strikes that deal 1d4 slashing damage on a hit. You can use your Dexterity or Strength modifier for the attack and damage rolls. At 9th level, attacks made with your claws that have advantage can critically hit on rolls of 19 and 20. At 13th level, you can use your claws to climb steeper surfaces, giving you climbing speed equal to your walking speed provided you attempt to climb with both hands free. 

Spine Launcher. One of your arms mutates to allow you to shoot spines out of your palm. The range of this weapon is 30/120 feet, and it deals 1d6 piercing damage on a hit. You can fire 20 spines before your body must make more. You regain all spines when you finish a short or long rest. At 9th level, the maximum amount of spines you can shoot is 30. At 13th level, the range increases to 80/320.

Killer Instinct

Starting at 9th level, the dark magic in your body hones your its natural instincts. You have advantage on Perception checks, you cannot be surprised, and your natural weapons count as magical for the purpose of overcoming resistance to nonmagical attacks and damage. 

You also have advantage on Intelligence (Investigation) checks to identify creature activity. 

Dark Shroud

At 13th level, you learn how to magically cloak yourself and camouflage with your surroundings. You can use a bonus action to turn invisible until you attack or until the start of your next turn. 

Once you use this feature, you cannot use it again until you finish a long rest. 

Stalker's Guile

At 17th level, your prey cannot hide anywhere from you, and your shadow-empowered characteristics reach their apex. You gain truesight out to 60 ft., and you can use Dark Shroud a number of times equal to your proficiency bonus. You also can't be affected by spells that alert others to your presence, or tell them your location.