Air Guardian Elma

Ephemeral Form. The elemental can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing. While doing so - it appears as a cloud of butterflies.

Permanent Featherfall. This creature cannot take damage from falling or being thrown.

Spellcasting. The guardian is a 12th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 16, +9 to hit with spell attacks). The guardian has following spells prepared:

Cantrips (at will): Minor Illusion, Fog Cloud 
1st level (4 slots): Thunderwave, Absorb Elements
2nd Level (4 slots): Gust of Wind, Misty Step, Levitate
3rd Level (4 slots): Sleet Storm, Pulse Wave, Lightning Bolt, Call Lightning
4th Level (3 slot): Storm Sphere, Fly (4th level version)
5th Level (2 slots): Conjure Elemental (Air only)

Multiattack. The guardian casts a spell, or it makes two attacks with its dagger/aero slice, or uses Butterfly Storm if available.

Butterfly Dagger. Melee or Ranged Weapon Attack: +5 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 7 (1d6 + 2) piercing damage plus 23 (6d6) lightning damage.

Aero Slice. Ranged Magic Attack. +9 to hit, range of 90 ft., 1 target. Hit: 15 magical slashing damage.

Butterfly Storm (Recharge 4-6). A 40 ft radius twister of whirling and crackling electric butterflies appears briefly at a location the guardian chooses within 150 ft of it that it can see. Creatures within the area must make a DEX save DC 16. On a failed save, the creatures are thrown in a random direction (prone) and take 40 (6d8) thunder damage. On a successful save, the creatures are not thrown and take half damage.