This is the so-called underground market, the black market.
There, they can buy some "dangerous" goods.
There is a saying that Hell, governed by demons, is the largest "black market."
For weak mortals, Hell is an extremely terrifying place, once you fall into it, you can never escape.
But for the strong, Hell is a decent plane.
Because of the nature of demons, transactions can still be conducted in Hell, and there is a certain level of security.
You might be robbed of your money by the buyer after the transaction, but you won't be forcibly killed during the sale.
There, dangerous merchants sell the world's most perilous and lethal "treasures."
Epic souls, creations of the Divine, fragments of Divine Artifacts, news of the fall of the Ancient Gods...
Weapons like the Magic Energy Cannon don't circulate much in the outside world; everyone holds onto them tightly and won't trade them at all.
But in Hell, a few Magic Energy Cannons are actually listed for sale at marked prices.
