Immutable Form.  The Creepwing Swarm is immune to any spell or effect that would alter its many forms.

Misery Loves Company. The Creepwing Swarm has advantage on attacks when within 5ft of another Creepwing Swarm.

Multiattack. The Creepwing Swarm makes one attack with its Grasping Claws and uses Chilling Harmony. If it hits with Grasping Claws and the target is grappled, it may also choose to Throw them.

Grasping Claws. Melee Weapon Attack: +7 to hit, reach 15 ft., one target. Hit: 21 (4d8 + 3) piercing damage, and if it is Large or smaller, the target must make a DC 15 Dexterity saving throw, or is grappled (escape DC 15 Strength/Dexterity Saving Throw).

Chilling Harmony. The Creepwing Swarm "sings" at up to three creatures that it can see within 30 feet of it. Each target must succeed on a DC 15 Wisdom saving throw or take 5 (1d6 + 2) psychic damage, and the target's AC is reduced by 1, this effect stacks with repeated exposure to Chilling Harmony. The affected creature may repeat this saving throw at the end of each turn. If a creature's saving throw is successful (after being affected by Chilling Harmony at least once), the creature is immune to Chilling Harmony for the next 24 hours.

Throw. The Creepwing Swarm will throw a grappled creature 20ft into the air and 10ft in any direction. The creature takes 7 (2d6)