Materials

What else is there to describe this?

Materials are the second requirement needed to upgrade your Base weapons.

Further classification of materials will be revealed in the upcoming future.

So far, we have hinted on the Gemstone Series as follows:-

Sapphire, Amethyst, Diamond, Ruby, Emerald

Hence, by buying these Materials + owning an OG/Armory Weapon, you'll have access to the Forge which will enable you to upgrade your Base Weapon.