You can't. They keep it all secret squirrel until a couple of months before they release something. The closest is the release schedule page here where I collate rumours:
Edit: This sounds like the Amber Temple, from Curse of Strahd.
"... "they were going up into the icy mountains, and this temple under a mountain that's basically become a repository of evil. There was this sect of good-aligned wizards and paladins who were keeping this temple, and all of the evil within it, trapped there, to keep the world from going, you know, crazy. Keep the world safe. But that was 400, 500 years ago. What's in there enow? Well, maybe the wizards have all died off. Maybe they sort of succumbed to the evil there. Who knows? But it's an interesting story, and that's a piece, or a fragment, of a story that is going to be important in the future."