Death Burst. When the swarm of mephits takes damage, it explodes in a burst of jagged ice. Each creature within 5 feet of it must make a DC 10 Dexterity saving throw, taking 4 (1d8) slashing damage on a failed save, or half as much damage on a successful one.

False Appearance. While the mephit remains motionless, it is indistinguishable from an ordinary shard of ice.

Innate Spellcasting  (at will). The mephit can innately cast fog cloud, requiring no material components. Its innate spellcasting ability is Charisma.

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny mephit. The swarm can't regain hit points or gain temporary hit points.

Claws. Melee Weapon Attack: +3 to hit, reach 5 ft., one creature. Hit: 21 (6d4 + 6) slashing damage plus 15 (6d4) cold damage, or  10 (3d4 + 3) slashing damage plus 7 (3d4) cold damage if the swarm has half of its hit points or fewer.

Frost Breath (Recharge 6). The mephit exhales a 15- foot cone of cold air. Each creature in that area must succeed on a DC 10 Dexterity saving throw, taking 30 (12d4) cold damage  or 15 (6d4) cold damage if the swarm has half of its hit points or fewer on a failed save. Taking half as much damage on a successful save