250px-Eye of the Beholder I PC box

This alternate reality game uses the hashtag #NoStoneUnturned for all communications between the players and the "puppetmaster".

The term "no stone unturned" is likely a reference to the game Eye of the Beholder, a video game released by SSI in 1991. In that game, the words "leave no stone unturned" are carved on a wall in the outer sanctum (level 11) of Xanathar the beholder, near the game's conclusion.


A partial screenshot from the game Eye of the Beholder where the text appears.

Based on that, the prevailing theory is that this alternate reality game is referencing the next adventure path that will take place in Undermountain.