When a world is as full to bursting with magic, monsters and mayhem as Nearth is, it's only natural that some people would make a living of dealing with such things - the siren's call of adventure is ever-tempting, after all, and even better if you can actually get paid for it.
...Unfortunately, it's almost just as natural the the most wealthy and powerful of Nearth would seek ways to exploit such people the same way they do everyone else. If there's a way to make someone do something for you for free, some blue-blood asshole has found it. Of course, given those first two premises, it is a perfectly natural consequence that adventurers would seek to band together and show the upper crust what's what, to ensure they're always given what they work for.
The Unioknights! are the first Adventurer's Union on Nearth, and these are the stories of how its members came together and went from being a bunch of talented gay lunatics to a deranged but formidable family.