Vangsluagh

Constant Racket. The vangsluagh has disadvantage on Dexterity (Stealth) checks.

Distracting Cacophony. The vangsluagh constantly emits a din of bleats, trills, and trumpets. A creature that casts a spell while it is within 30 feet of the vangsluagh must make a DC 13 Intelligence, Wisdom, or Charisma saving throw. (The type of saving throw required is dependent on the spellcasting creature's spellcasting ability score.) On a failed save, the spell isn't cast, and the spell slot isn't expended. In addition, a creature that starts its turn within 30 feet of the vangsluagh and is maintaining concentration on a spell must succeed on a DC 13 Constitution saving throw or it loses concentration on the spell.

Multiattack. The vangsluagh makes two tentacle lash attacks.

Tentacle Lash. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 12 (2d8 + 3) bludgeoning damage.

Sonic Bullet. Ranged Spell Attack: +5 to hit, range 120 ft., one target. Hit: 10 (3d6) thunder damage, and the target must make a DC 13 Constitution saving throw or be deafened until the end of its next turn.

Agonizing Trill (Recharge After a Short or Long Rest). The vangsluagh increases the pitch of its cacophony to deadly levels. Each creature within 30 feet of the vangsluagh must make a DC 13 Constitution saving throw. On a failure, a creature takes 10 (3d6) thunder damage and is stunned for 1 minute. On a success, a creature takes half the damage and isn't stunned. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.