In the middle of a zombie apocalypse, a war between good vs evil, or far beyond where any normal human should be. You can find them. Inside their domain, these beings often pass themselves off as just a 'humble merchant'. Trading goods, buying junk, and often selling rare, sometimes mythical, items. That is who you are. But you aren't just a 'mere human merchant' are you? Your shop is your domain. And in your domain you are untouchable, but so too are all customers within your store. And what a store it is.
Within your establishment, violence and harm are strictly forbidden, rendering all who enter temporarily invulnerable while perusing your wares. As the owner, you possess the authority to forcibly expel any individuals within your store at any time, as well as deny entrance to those you wish to keep out. Thievery, both by yourself and your customers, is strictly prohibited within the store. Furthermore, the environment of your shop is perpetually safe for anyone who enters.
Your mastery as a merchant extends to accurately determining the market price, within your current universe, of any item you lay your eyes upon. Although you are responsible for stocking your store, any non-unique or non-one-of-a-kind items you include in your inventory will automatically replenish themselves once purchased by a customer. Additionally, you have the ability to purchase items from others, provided that they willingly and freely desire to sell said items, without any external influences compelling them. Currency can be effortlessly converted from one form to another at your discretion. The nature of your shop and the manner in which you sell and buy goods is entirely customizable, subject to your own preferences. You can freely alter its appearance, ranging from a modest outdoor stall to a magnificent emporium. Perhaps you might consider presenting your goods through a grimoire that contains comprehensive information about each product, or you could employ a holographic or gaming system-style shop menu that materializes before the customer's eyes when they wish to make a purchase.