Bereginyas

Foul Form. The bereginyas's semi-solid form emits poisonous gases. Any creature that starts its turn within 5 feet of the bereginyas must succeed on a DC 14 Constitution saving throw or be poisoned. A creature that succeeds on this saving throw by 5 or more is immune to the bereginyas's Foul Form for the next 24 hours.

Multiattack. The bereginyas makes two Claw attacks. If both attacks hit the same target, the bereginyas attaches to the target. While attached, the bereginyas can use only the Smother action, and it moves with the target whenever the target moves, requiring none of the bereginyas's movement. The bereginyas can detach itself by spending 5 feet of its movement. A creature, including the target, can take its action to detach the bereginyas by succeeding on a DC 14 Strength check.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage plus 4 (1d8) poison damage.

Smother. While attached to a creature that isn't a Construct or Undead, the bereginyas extends a tendril of poisonous gas down the creature's throat. The creature must make a DC 14 Constitution saving throw. On a failure, it takes 22 (5d8) poison damage, immediately runs out of breath, and begins suffocating. On a success, it takes half the damage, doesn't run out of breath, and isn't suffocating. Suffocation ends if the creature dies, if the bereginyas is removed from the creature, or if the bereginyas is killed. A suffocating creature that fails this saving throw reduces its remaining rounds of breath by 1.