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Sinister Awareness
At 11th level, you learn to extend your supernatural abilities into your senses. You may spend 4 exertion points to gain Truesight with a range of 30 feet for one minute. While this ability is active, you may attack creatures on the Ethereal Plane (such as ghosts or creatures under an etherealness effect).
While this ability is active, you can use this awareness to perceive the flow of life force through creatures and disrupt it with your strikes. Attacks you make with adept weapons or your unarmed strikes do additional necrotic damage equal to your martial arts die.
Killing Touch
At 17th level, you learn the most terrifying technique of all, the killing touch. When you hit with a melee attack, you may declare that you are using your killing touch ability. If you do, the creature you struck has fewer than 100 hit points, it is immediately slain. If the creature has 100 hit points or more, your attack deals damage as normal and the creature also takes an additional 50 points of necrotic damage. Once you have used this ability, you cannot use it again until you have finished a long rest.