Breathsnatcher

Bedridden. The breathsnatcher always succeeds grapple checks against prone creatures.

Broken Mind. The breathsnatcher is immune to being charmed, is resistant to psychic damage, and its behaviour cannot be influenced magically. A greater restoration spell deactivates this feature for 1d4 hours, after which it reactivates.

Cleansing. The breathsnatcher automatically knows the location of any creature that regains hit points in any way within 60 feet of it. The breathsnatcher has advantage on checks made to locate creatures damaged by it in the last hour.

Graceful Landing. When the breathsnatcher falls, the damage it takes is reduced by 27 (5d10).

Last Breath (Mythic Trait; Recharges after a Short or Long Rest). When the breathsnatcher is reduced to 0 hit points, it does not die or fall unconscious. Instead, all creatures within 30 feet of it must make a DC 15 Constitution saving throw. The breathsnatcher gains 50 temporary hit points for each creature that failed the saving throw, who fall unconscious until the start of their next turn. While the breathsnatcher has these temporary hit points, it can't gain any more, and it can't regain hit points in any way. When all of these temporary hit points are lost, the breathsnatcher dies.

Thanataphobia. Each time a creature is hit by the breathsnatcher, the breathsnatcher gains a +1 bonus to attack and damage rolls against that creature. If the creature regains hit points in any way, this bonus ends.

Undead Fortitude. If damage reduces the breathsnatcher to 0 hit points, it must make a Constitution saving throw with a DC of 8 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the breathsnatcher drops to 1 hit point instead.

Undead Nature. The breathsnatcher can doesn't need to eat, breathe, drink, or sleep.

Multiattack. The breathsnatcher makes three Bonesaw attacks.

Snatch Breath. The breathsnatcher manipulates the breathing of a creature it is grappling, causing it to begin suffocating. If the breathsnatcher does not use this action on subsequent turns, the creature stops suffocating. A creature brought to 0 hit points in this way immediately dies, and this grants the breathsnatcher temporary hit points equal to the creature's level or CR.

Bonesaw. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 5 (1d8 + 1) slashing damage. 

Blink. The breathsnatcher magically moves, along with any equipment it is wearing or carrying, up to 30 feet to an unoccupied space. This is not restricted to vision, and the breathsnatcher is not affected by the environment (walls, difficult terrain, etc.). After blinking once, the breathsnatcher may, as part of the same bonus action, immediately blink to a second location within 15 ft. At the end of their turn, the breathsnatcher will become Incapacitated until the end of their next turn if they blinked twice, or until the start of their next turn if they blinked once. While Incapacitated in this way, the breathsnatcher's movement speed is halved.

Telekinetic Shove. Up to two creatures the breathsnatcher can see must succeed on a DC 15 Strength saving throw or be moved up to 10 feet. A creature can willingly fail this save.

Hover. When the breathsnatcher begins to fall, they instead hover in place.

The breathsnatcher can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The breathsnatcher regains spent legendary actions at the start of its turn.

Move. The breathsnatcher moves up to its speed.

If the breathsnatcher's mythic trait is active, it can use the options below as legendary actions, as long as it has temporary hit points from its Last Breath.

Blink Attack. The breathsnatcher takes its Blink bonus action and then makes a Bonesaw attack against a creature within 5 feet of it.

Strike of the Wind (Costs 2 Actions). All creatures within a 5-foot-wide 20-foot-long line must make a DC 15 Dexterity saving throw. A creature takes 3d10 bludgeoning damage on a failed save, or half as much on a successful one.

Unnerve (Costs 2 Actions). All creatures of the breathsnatcher's choice that are within 30 feet and aware of it must make a DC 15 Wisdom saving throw or be Frightened of the breathsnatcher until the end of their next turn.