You should always ask from proof at the seller only than you can know its good and okay.
Yes that's true dark marketplace is not safe at all. Just like if you are going to have a transaction in deep web.
Tendency is that hackers / scammers are going to steal your information and they are just going to save it on their database.
Or even they use it for illegal transactions.
Like silkroad 2 lol,i remember my buddy got scammed there for about 2k of $,he wanted to cry so much back then
Honestly its hard to trust people in that places dark market or deep market.. almost all people there are hackers and scammers..
That is the reason most people do not use the dark market place. It is also illegal to sell certain goods.