Adventurers pick things up. Well, to be more accurate, adventurers pick everything up. No matter how utterly useless some random piece of junk may seem while exploring the world, no adventurer worth their salt is going to leave it behind. Even though the stitches in their pack are straining with the weight of all the stuff they have already gathered, no adventurer can pick up any piece of loot without thinking, “I might need this!”
Besides, what would be the point of punching and grunting your way through a dungeon, nearly getting your extremities bitten off by zombies or goat-men (or zombie goat-men) without the intention of coming out the other side with your spine nearly bent in half by a satchel full of invaluable ancient treasures (and some pointless crap)?
Despite their infernal appearance, the merchants of the Void Society always conduct themselves with deference and unwavering politeness. They speak in proper accents and are exceptionally gregarious and well-mannered.
The Void Society is politically neutral, and deal with all societies equally. They have no interest in the ongoing hostilities between the major factions, and all of their customer transactions are conducted with equal fairness and amity.
The members of the Void Society speak rarely of themselves as individuals, and have little to say of the struggles they endure in their home plane of existence. Every so often, a jagged rift is torn open from the Void into the world of Entrath, and insane, tentacled monsters slither into reality. These horrific beasts of pure madness are but a glimpse of what the Void Society must eternally battle to preserve their very existence.
Fortunately, the Void Society have devised a clever system of alchemy that is capable of taking even the most worthless doodads found in the dark, forgotten realms by intrepid adventurers and converting them into viable materials they use in their never-ending conflicts in the Void. This allows Entrath to have a vibrant economy, as the Void Society gladly trades gold for whatever valuables are brought to them. And, for a small fee, the Void Society will even teach others how to manipulate the alchemical formulas they invented to break items down into their ethereal components, which can then be reassembled into something completely different (maybe even something that has never existed before).
The Void Society have operated within Entrath for so long, they are trusted to run Entrath’s only inter-faction bazaar, where items of true value can be traded in an auction style format.