Death Burst. When the arch-mephit dies, it explodes into a burst of jagged ice. Each creature within 10 feet of it must make a DC 14 Dexterity saving throw, taking 7 (2d6) slashing damage on a failed save, or half as much damage on a successful one.
False Appearance. While the arch-mephit remains motionless, it is indistinguishable from an ordinary ice formation.
Innate Spellcasting. The arch-mephit's innate spellcasting ability is Wisdom (spell save DC 12). The arch-mephit can innately cast the following spells, requiring no components:
At will: Color Spray, Dancing Lights, Fog Cloud, Ray of Frost
1/day each: Ice Knife
Multiattack. The arch-mephit makes one attack with it's claws. If that attack hits, the arch-mephit can make one freeze attack against the same target.
Claws. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6+2) slashing damage plus 3 (1d4+1) cold damage.
Freeze. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (2d4+1) cold damage, and the target must succeed on a DC 10 Constitution saving throw or be petrified for the next 3 turns. The target can repeat the saving throw at the end of each of it's turns, ending the effect on a success.
Frost Breath (Recharge 6). The arch-mephit exhales a 20-foot cone of cold air. Each creature in that area must succeed on a D 14 Dexterity saving throw, taking 7 (1d8+3) cold damage on a failed save, or half as much damage on a successful one.