Great Cat Kingdom

Kitty Kingdom was a feline theme Guild that existed in YGGDRASIL.

Background
Kitty Kingdom was a guild that created NPCs based on cats or other feline creatures.

The Undead King Arc
When Momonga noted that not every NPC in a guild was designed for battle, he look towards a certain guild like the Kitty Kingdom as a prime example, where fielded no NPCs other than mainly cats or cat-related creatures.

Strength
While the guild's overall strength remains a mystery, Kitty Kingdom was shown to be capable of conquering a castle dungeon and then converting it into their guild base.

Trivia

 * So far, Kitty Kingdom was mentioned only once in Light Novel Volume 1.