Burst of filth. When the wretched dragon drops to 0 hit points the dragon explodes in a burst of filth and each creature within 15 ft of the dragon must make a dc 15 con save or take 25 (5d10) poison damage and the target is poisoned for 1 minute and can remake the save at the end of their turn. On a successful save the target takes half damage. 

Multi attack. The dragon makes 1 bite attack and 2 claw attacks. 

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., 1 target. Hit: 11 (2d6 + 5) [piercing] damage plus 10 (2d10) necrotic damage and the target must make a dc 15 con save or if possible the dragon uses the curse of the evil jaw. 

Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 13 (2d8 + 5) [slashing] damage. 

Curse of the Evil jaws (Recharges after a Short or Long Rest).With a bite, the dragon uses its bite, but on a failed save, the creature is also cursed with magical deformities. While deformed, the creature has its speed halved and has disadvantage on ability checks, saving throws, and attacks based on Strength or Dexterity.

The transformed creature can repeat the saving throw whenever it finishes a long rest, ending the effect on a success.

Psychic wind Breath (Recharge 5-6). The dragon exhales a gust of psychic infused wind in a 60-foot cone. Each creature in that area must make a DC 15 intelligence saving throw, taking 54 (12d8) psychic damage and the target is pushed 25 ft in any direction of the dragons choice on a failed save, or half as much damage and instead of pushed 25 ft they are pushed 15 ft on a successful one.