Crimson Jaw

Corrupted Hunger
Whenever the Crimson Jaw drops a creature to 0 HP, it regains 10 HP and gains advantage on its next attack roll before the end of its next turn.

Mask of Butchery (1/Day)
Once per day, the Crimson Jaw can unleash a wave of psychic agony. All creatures within 10 feet must succeed on a DC 14 Wisdom saving throw or take 13 (3d8) psychic damage and be Frightened until the end of their next turn. On a success, creatures take half damage and are not frightened.

Scent of Weakness
The Crimson Jaw has advantage on attack rolls against any creature that is bloodied (below half HP).

Multiattack. The Crimson Jaw makes two attacks: one with its Maw and one with a Tendril Lash.

Maw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target.
Hit: 15 (2d10 + 4) piercing damage. If the target is Medium or smaller, they must succeed on a DC 13 Strength saving throw or be grappled (escape DC 13).

Tendril Lash. Melee Weapon Attack: +6 to hit, reach 10 ft., one target.
Hit: 10 (2d6 + 4) slashing damage. If the target is grappled by the Crimson Jaw, the attack deals an additional 5 (1d10) necrotic damage.