So, I ventured into the subreddit due to a link upthread.
you buy a black credit card that is sold in very limited amounts on the store every now and then. It’s around 35USD if i remember correctly. That will get you emails with the time and date. However it’s not a secret and the date and place was public knowledge as it has been posted on this site multiple times. I believe everyone is welcome to show up at the meeting, they ask you to bring a friend in the emails.
concierge members (those who put more than 2000$ in the development of the game) get some special attention, like being able to fast track customer support requests, early access to sales, ordering besaid “black metal concierge business card” and sometimes being invited to a popup event with the devs. (like the public beergarden events around gamescom/citizencon, just a bit smaller)
It’s a meta-scam. Scam squared. Those who have bought into the scam can pay extra to bring a friend along to a ponzi scheme sales pitch. Bernie Madoff would be proud.