Guns were originally created in Karaten - a simple to use weapon that fires 'bullets' of the user's focus, basically allowing anyone to use magic. However, they were not meant to be public - which is unfortunate, as the technology was stolen from under their noses. Nowadays, knock-offs can be found in seedy areas, gradually making the once-secret weapons more available, even to adventurers.
Arcane Shells, however, are less common, despite amplifying the power of guns significantly. In part due to being less understood, and partially because they significantly drain the user more than a regular gun, giving rise to the fear that they can make your lifespan shorter.
Has a variety of shells with different useful effects and debuffs.