Hyakki Yagyō

One night a group of demons patrolled through a significant part of Fiore. It is said that any one who got in the path of the demons were instantly killed by the demons. That group of demons is now known as Hyakki Yagyō (百鬼夜行, "Night Parade of One Hundred Demons") and the leader of this terrifying group is now known as Nurarihyon.

Nurarihyon
Nurarihyon is by far the strongest member of the Hyakki Yagyō. He is highly respected by the demons in his guild, he is even respected by The Four Great Generals.

The Four Great Generals

The Four Great Generals are four very powerful co-leaders of the Hyakki Yagyō. They are Nurarihyon's most trusted allies. All four of them are an Etherious instead of a regular demon like the rest of the demons in this guild. The most powerful of The Four Great Generals is a girl that goes by the name of Yuki Onna. It is said that just her presence alone can cause the temperature to drop to below zero. The second strongest is an Ox type demon that goes by the name of Gyūki. Gyūki is said to have immense physical prowess. He doesn't use magic, but instead uses his physical strength and combat skills to quickly dispose of an enemy.

Trivia

 * This guild is based off of a group of demons in Japanese folklore.