Cursed Spirit of Nightmares

Aspect of Terror: Creatures within 30 feet on the CSN's turn must make a DC 13 WIS save or be frightened until the end of its next turn

Master of Terror: Creatures that would be immune to frightened when within 15 feet of the aspect of terror instead have advantage on saving throws against frightened

What hides in the dark: This creature is invisible outside of combat when in darkness but can be seen out of the corner of creatures eyes 

Terrifying Revival: When this creature is reduced to 0 hp (not by radiant damage), this creatures body regenerates and contorts in a terrifying way, CSN is healed to 30 HP and retriggers "Aspect of Terror"

Specialized Terror. Create an illusion to torment one specific person, choose a victim within 30 feet to make a WIS DC 13 save, on a fail they are frightened until the end of their next turn and take 1d10 psychic, if already frightened then they become prone in terror for 1 rounds and take 2d10 psychic damage, if already prone from this specific action  take 5d10 psychic damage

Rip and Tear. Melee Weapon Attack: +7 to hit, reach 10 ft., 1 target. Hit: 10 (2d4 + 4) slashing damage. Creature upon being hit by "Rip and Tear" must make a DC 10 con save or gain a level of exhaustion which is removed upon recieving any form of healing

Agonizing Screech. Upon taking damage you may let out a gut wrenching screech, creatures within 15 feet must make a DC 15 con save or take 2d6 thunder damage 

This creature gains 1 legendary action per round when at half health or lower

Specialized Terror (Costs 1 Action). Use the specialized terror action 

Piercing Gaze (Costs 1 Action). The CST gives a piercing gaze to a creature within 60 feet, that creature must succeed a DC 13 WIS save or become frightened until the end of its next turn and take 2d10 psychic damage, half damage on save and no frightened 

Ferocious Leap (Costs 1 Action). Creature leaps up to 15 feet and uses rip and tear