The Adventurer's Guild is the main guild that the protagonists belong to.
It is unknown when the Adventurer's Guild was established but it existed more than 60 years prior to the storyline.
The main base of the guild, Sky Axis, is located in the West Capital Tenzik. Here is where the Seven meet and talk about important matters.
The Adventurer's Guild is similar to your typical RPG game in which an Adventurer can choose to which class they want to pursue. The known classes are Fighter, Wizard, Warrior, Monster User, Magic Fighter and Magic Warrior. Each classes have their own type of badge to distinguish them from each other.
The Guild seems to be world wide seeing how it needs to situate sub-guilds in different parts of the world. The sub-guilds have their own Chiefs. This way they can assign jobs easier. It is shown that jobs might differ from monster slaying to handing out a tissue.
The Guild establishes the levels of both Adventurers and Monsters. Adventurer's level are based numerically with every starting Adventurer at Level 10 and with it increasing as a character gets stronger. The highest level seen so far is 45 belonging to Blue. It is possible to decline in level as Keel ended up being a level 0 because of multiple dine-and-dashes. Monsters are based on alphabetical levels starting with G and ending with S. Some monsters might be from a lower class but may manage to become stronger than their standard level.
If Adventurers wish to they can form a party and take on jobs. The level of job is the average of the members' levels together.