Story (behind the shopkeep): Once a scary and feared entity, now reduced to selling items to make some amount of money to pay back his guards (since there keeping things together in his universe). Void can be found in the lobby and will allow you to buy Flashlights, Med kits, and a mystery perk which will give you a random advantage along with where you can buy monsters and such from him.
BTW it's supposed to be a green visor hat that he wears kinda like a poker hat along with his black bowtie