Katress Hair is a material obtained exclusively from a Pal called Katress, which is considered to be a common material nonetheless.
This is easy to farm once you are around level 20 to 25 and higher as Katress may be commonly found within such level ranges.
While it is said that Katress Hair is used to make clothing, it is currently only used to craft one item in the game until updates add more uses for it.
How To Get Katress Hair?
Defeating Katress and Katress Ignis
Katress hair can only be obtained from Katress, which is a Pal that spawns specifically at night in only a couple of regions of the map. (There is a 50% chance to drop)
These Pals only spawn during the night and will stop spawning once it is morning, which makes it important to hunt them only during such times.
There is also a Katress Boss in the Sealed Realm of the Invincible dungeon at Marsh Island but this variant is known to not drop Katress Hair. (It drops Precious Pelt instead)
Katress Location
Katress will often spawn around the Moonless Shore (more abundant in this location) and will also spawn in the Verdant Brook.
During the night, you will see several of them roaming around but you should be careful as they can be quite aggressive.
A good way to search for them would be to fly around at a low altitude so you can easily get around and spot them. (You can even defeat them with a flying Pal)
Katress Hair Uses
Katress Hair is used to craft the Katress Cap, which is a cap that is shaped like a Katress (A witch hat with Katress ears) that can be worn by the player.
A Katress Cap can be equipped in your Head Armor slot and will provide you with Level 1 Dark Damage Reduction.
Aside from its passive, the Katress Cap also provides your character with 20 Defense and 60 Health when they have it equipped.
Aside from the Katress Cap, this material may also be used to craft a Speed Remedy, which increases the Work Speed of your character.
Multiple Speed Remedies may be crafted and consumed to reach a certain limit, which can be crafted later when you have a lot of this material.
Verdict
Since Katress Hair is only used for crafting the Katress Cap, it is only useful for those who intend on using the Head Armor for its stats or appearances.
If Katress do not spawn in their regular zones, you may need to clear out some of the other Pals in the area or continue exploring until you run into them.
Katress will not always drop Katress Hair and are often guaranteed to drop Leather most of the time but the chances to get this material are still good.