Hello all,
As I have not properly statted up a brand new monster in about 15 years, I would very much like a critique of my effort, as well as suggestions for changes and improvements both in editing and actual details.

The Kamaitachi is a trio of weasels from Japanese mythology that were used to explain the cause of frostbite. Unfortunately I am unable as of yet to provide links, but they are easy to find.

Spoiler: Campaign related info for the interested
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The campaign is a 3.5 oriental adventures campaign based heavily on Japan in terms of social structures and creatures. Since none of my friends are very experienced I helped with all character creations to prevent too many bad choices overall.
Characters were made with a relatively high point buy and tend to be fairly strong.
The party is currently level 4, but will probably be 5 by the time they encounter this.
The party setup is as follows:
Samurai - Mainly focused on using Katana 2 handed,
Ranger - Focused mainly on bows,
Rogue - Mainly sneak attacks stuff,
Shaman 1 - Mainly uses buffs and uses a Naginata in combat,
Shaman 2 - Specced for summoning.
It is generally fine if not all party members are well suited to every encounter, since I try and generally vary them with encounters that showcase different character strengths.

I generally allow infinite healing outside of combat, since I like challenging them with in game time limits, which causes them to spend a while between rests, and causes spell resources to feel move valuable.

Additionally I home ruled move silently and hide into 1 skill, as well as spot and listen into 1 skill to help encourage the ranger and rogue to act as scouts.

The general plan for this encounter is to have it occur periodically as they traverse a frozen land, where the players can be attacked at any time.
This will require them to form a plan and figure out some way to prevent the Kamaitachi being revived. There will only be a single trio of Kamaitachi, and all encounters after they are defeated will have a reasonable diplomatic solution.
The general intention is to create a dangerous atmosphere where the party may be attacked at any time, by highly mobile enemies, which can appear and disappear with relative ease.


Now without further ado, the Kamaitachi -
Toppu -
Size/Type: Medium Magical beast (Spirit)
Hit Dice: 7D10 + 14 (52 hp)
Initiative: +5
Speed: 40 ft. (8 squares)
Armor Class: 19 (+5 Dex, +4 natural), touch 15, flat-footed 14
Base Attack/Grapple: +7/+9
Attack: Bite +9 melee (1d6+3)
Full Attack: Bite +9 melee (1d6+3)
Space/Reach: 5 ft./5 ft
Special Attacks: Gust breath
Special Qualities: Darkvision 60, scent, Disperse into snow, Cold subtype
Saves: Fort +7, Ref +10, Will +3
Abilities: Str 14, Dex 20, Con 14, Int 8, Wis 12, Cha 11
Skills: Hide +12, Listen +1, Move Silently +12, Spot +1
Feats: Dodge, Mobility, Combat expertise
Environment: Cold climates, only in temperatures below freezing.
Organization: Always with Kama and Nanko
Challenge Rating: 3 (alone) 6 with Kama and Nanko
Treasure: None
Alignment: Always neutral evil

Kama -
Size/Type: Small Magical beast (Spirit)
Hit Dice: 6D10 + 6 (39 hp)
Initiative: +6 (Special)
Speed: 60 ft. (12 squares)
Armor Class: 18 (+6 Dex, +2 natural), touch 16, flat-footed 12
Base Attack/Grapple: +6/+6
Attack: Claws +6 melee (1d4+1)
Full Attack: 2 Claws +6 melee (1d4+1)
Space/Reach: 5 ft./5 ft.
Special Attacks: Follow Toppu, Pounce
Special Qualities: Darkvision 60, scent, Disperse into snow, Cold subtype
Saves: Fort +6, Ref +11, Will +3
Abilities: Str 12, Dex 22, Con 12, Int 8, Wis 12, Cha 11
Skills: Hide +12, Listen +1, Move Silently +12, Spot +1
Feats: Dodge, Mobility, Spring attack
Environment: Cold climates, only in temperatures below freezing.
Organization: Always with Toppu and Nanko
Challenge Rating: 3 (alone) 6 with Toppu and Nanko
Treasure: None
Alignment: Always neutral evil

Nanko -
Size/Type: Small Magical beast (Spirit)
Hit Dice: 6D10 (33 hp)
Initiative: +6 (Special)
Speed: 60 ft. (12 squares)
Armor Class: 18 (+6 Dex, +2 natural), touch 16, flat-footed 12
Base Attack/Grapple: +6/+6
Attack: Bite +6 melee (1d3)
Full Attack: Bite +6 melee (1d3)
Space/Reach: 5 ft./5 ft.
Special Attacks: Follow Kama, Frostbite salve
Special Qualities: Darkvision 60, scent, Disperse into snow, Cold subtype
Saves: Fort +5, Ref +11, Will +4
Abilities: Str 10, Dex 22, Con 10, Int 10, Wis 14, Cha 13
Skills: Hide +12, Listen +8, Move Silently +12, Spot +8
Feats: Dodge, Mobility, Spring attack
Environment: Cold climates, only in temperatures below freezing.
Organization: Always with Toppu and Kama
Challenge Rating: 3 (alone) 6 with Toppu and Kama
Treasure: None
Alignment: Always neutral evil


Description:
The Kamaitachi are a trio of winter spirits appearing in the form of white weasel like creatures. These creatures prefer to slowly chip at their prey across many hours letting their frostbite stack up until eventually their prey succumbs in weakness and they can gorge on the frozen flesh.

Toppu – An unusually large weasel with an overly large belly, it’s slow and ponderous appearance belies an unnatural agility. Its eyes are foggy blue of a winter sky.

Kama – A particularly thin weasel, 2 large curved blades extend from its paws in a shape similar to a kama. Its eyes are a clear blue with a small sparkle in the center like ice sparkling in the sun.

Nanko – The smallest of the trio, nanko is runty in appearance, and carries behind it a small white gourd. Its eyes are the clear white of snow.

Combat:
In combat the Kamaitachi will always prefer to have Toppu start with his gust breath, followed by Kama attacking prone targets, and Nanko finishing off by applying his salve to Kama’s target. Should one of them be knocked out or after a few rounds the Kamaitachi will retreat and attempt to attack after the frostbite starts taking its toll.

If the kamaitachi are forcibly separated they will attempt to recover the missing member. If Nanko is killed and there are no usages of the frostbite salve the remaining Kamaitachi will fight to the death.

Gust Breath – As a standard action Toppu takes a deep breath and exhales a cone of wind 25 feet in length. Creatures in the cone must make a fortitude save (DC15) or be knocked prone. Large creatures or larger are immune to this effect.

Pounce – If Kama charges a foe, it can make a full attack, including both claws.

Frostbite Salve – On his turn Nanko can use a standard action to apply his salve to any wounds caused by kama, immediately healing all damage done by them.
After an hour a fortitude save must be made (DC 13) or all damage cured by the salve is instead taken as temporary dexterity damage, only 1 damage will be taken on a successful save.
As an alternative use, the frostbite salve can be applied to any of the Kamaitachi, curing them for 1d8+5 hp. This salve can be used to revive any of the Kamaitachi from death.
The gourd can contain up to 10 usages at a time, and can be slowly refilled by Nanko using his saliva.

Disperse into snow – Once per round while moving across snow the Kamaitachi can attempt to disappear into it, hiding without using an action. They can attempt to hide with a -10 on the roll.

Follow – Instead of rolling for initiative Kama and Nanko can instead choose to have their initiative be 1 behind Toppu and Kama respectively. They can then use the new initiative as though they have rolled it.

Hope you enjoyed reading it, please leave some comments ,suggestions and critiques if you have any.
Also feel free to use this encounter in your campaign and if you do, I'd love to hear how the party dealt with it.