Air Elemental Swarm

Air Form. The swarm can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Magical Weapons. The swarm's weapons count as magical for the sake of overcoming damage resistance.

Swarm. The swarm can occupy another creature's space and vice versa. The swarm can't regain hit points or gain temporary hit points.

Multiattack. The swarm makes two slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 28 (4d8 + 5) bludgeoning damage.

Whirlwind (Recharge 4–6). Each creature in the swarm's space must make a DC 17 Strength saving throw. On a failure, a target takes 32 (6d8 + 4) bludgeoning damage and is flung up 20 feet away from the swarm in a random direction and knocked prone. If a thrown target strikes an object, such as a wall or floor, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 17 Dexterity saving throw or take the same damage and be knocked prone.

If the saving throw is successful, the target takes half the bludgeoning damage and isn't flung away or knocked prone.

Lightning Strike (Recharge 5-6). The swarm makes a slam attack. On a hit, the target takes an extra 18(4d8) lightning damage, and the target must succeed on a DC 17 Constitution saving throw or be stunned until the end of the swarm's next turn.