Kamaitachi

Air Form (Wintry Swirl Form Only). The kamaitachi can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Concealing Snow (True Form Only). As a bonus action, the kamaitachi sheathes itself in blowing ice and snow, causing attack rolls against it to have disadvantage. The kamaitachi can use this trait only if it is in snowy terrain. Flyby (Wintry Swirl Form Only). The kamaitachi doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Keen Smell. The kamaitachi has advantage on Wisdom (Perception) checks that rely on smell.

Shapechanger. The kamaitachi can use its action to polymorph into a swirl of wintry weather. It can revert back to its true form as a bonus action. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form when it dies. While a wintry swirl, it has a flying speed of 40 feet, immunity to the grappled, petrified, prone, and restrained conditions, and resistance to bludgeoning, piercing, and slashing damage from nonmagical attacks.

Snow Devil (Wintry Swirl Form Only). Until it attacks or uses Wintry Assault, the kamaitachi is indistinguishable from a natural swirl of snow unless a creature succeeds on a DC 15 Intelligence (Investigation) check.

Multiattack. The kamaitachi makes two sickle paw attacks.

Sickle Paw (True Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 18 (4d6 + 4) slashing damage.

Wintry Assault (Wintry Swirl Form Only). Each creature in the kamaitachi's space must make a DC 15 Dexterity saving throw. On a failure, the creature takes 9 (2d8) slashing damage plus 9 (2d8) cold damage and is blinded until the end of its next turn. On a success, it takes half the damage and isn't blinded.