From here https://www.reddit.com/r/DarkNetMarkets/wiki/index/relevantsubs#wiki_related_.onion_forums.3A
The Cave: http://kwemv6xssdwyutoc.onion
The Vault: http://vault43z5vxy3vn3.onion/forum/
They are both not working and have been gone since months it seems.
Did they move?