Whenever Bliz adds secrets into the game, it really gets the community going and is generally pretty cool.
Another area of the community that’s a bit underserved is Lore. I personally think folks who enjoy secrets in the world, generally engage with the Lore as well.
A cool combo could be for a “library” feature be added. You can have a private and public section. Private could be all the lore books you pickup in the world. Your own collections.
The public books though would be public to everyone in the game. They’d all be greyed out, but once someone in your region finally finds a book, it unlocks in the public library (and it’s location). Bliz could continuously drop lore books at random times, and expand different lore strings that they’ll eventually use for future expansions, but it’s just fun information that the community unlocks together. You can tie some cosmetics to certain book finds too.