Cursed Bulette

Deadly Curse. The bulette's body is enraptured by necrotic energy. Every melee attack made by this creature deals necrotic damage to some degree. All necrotic damage dealt to enemy creatures lowers their Maximum Hit Points by that damage value until they complete a Long Rest.

Necrotic Detonation. If the bulette reaches 0 Hit Points, it explodes in a 30ft radius. All creatures within that radius must make a DC 17 Dexterity Saving throw. On a failed save, the creature takes 18 (3d12) Necrotic damage or half as much on a successful Save.

Bite. Melee Weapon Attack: +9 to Hit, 1 target. Hit 13 (2d12) Piercing damage and 6 (1d12) Necrotic damage.

Tail Slam. Melee Weapon Attack:  +7 to Hit, 1 target. Hit 10 (1d12+4) Bludgeoning damage and 5 (1d8) Necrotic damage.

Necrotic Blast. Ranged Weapon Attack: +8 to hit, range 40/120 ft., 1 target. Hit: 13 (2d12) Necrotic damage.

Smoke Shroud. The bulette releases a greyish-purple cloud of smoke from its mouth, completely enveloping it. Creatures making attacks against the bulette have Disadvantage and the bulette has Advantage on attacks it makes against creatures that cannot see through the smoke. The cloud of smoke remains for three rounds, however it can be dissipated through a breeze equally or more powerful than a Gust cantrip. 

Cone of Sleep (Recharge 5-6). The bulette breathes out a swirling cloud of greyish-purple gas and smoke in a 40ft cone in front of it. Each creature within the cone must make a DC 17 Constitution Saving Throw or fall unconscious. They do not drop to 0 hit points, however, attacking creatures still gain the benefits of an unconscious target. Affected creatures may repeat the Saving Throw at the end of their following turns.

Deadly Leap. If the bulette jumps at least 15 feet as part of its movement, it can then use this Action to land on its feet in a space that contains no more than one creature of medium size or up to three creatures in small or tiny size. Each of those creatures must succeed on a DC 17 Strength or Dexterity saving throw (target's choice) or be knocked prone, become restrained by the bulette, and take 13 (3d6 + 4) Bludgeoning damage plus 13 (3d6 + 4) Slashing damage. On a successful Save, the creature takes only half the damage, isn't knocked prone, and is pushed 5 feet out of the Bulette's space into an unoccupied space of the creature's choice. If no unoccupied space is within range, the creature instead falls prone in the Bulette's space, but is still not restrained.

The bulette can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The bulette regains spent legendary actions at the start of its turn.

Counter-Attack (Costs 1 Action). After an enemy creature lands an Attack on their turn, the bulette may make a Bite or Tail Slam Attack against that creature.

Draining Surge (Costs 2 Actions). The bulette pulls the life force out of the surrounding plants and animals to heal itself 25 (4d10+5) Hit Points. Enemy creatures are not susceptible to damage from this maneuver.