Dark marketplaces are bad places lol most people there are there for the illegal business so.. alot of undercover agents aswell. I've heard about this new black market called theMarketplace but it's pretty difficult to enter or something, might be worth reading up on if you are interested.
i guess some of the links on the deepweb that is indexed as a blackmarkets are just a trap made by the undercover agents or the FBI . i have tried to surf the darkweb and entered some drugs and weapon markets just to see if there are actually a illegal stuffs that are being sold there .