I had started The Dreamhold several times since its original release in 2004, but never finished it until its recent release on iOS. This release has Game Center achievements, and at least three of them are hidden.
I discovered one of the hidden ones:
Apparently as you progress through the game, there is an increasing (though always small) chance that going northeast from "Curving Hall at Pedestal" will take you to the Stone Spire instead of the Harp Chamber. Entering the Stone Spire unlocks the "Precarious Perch" achievement.
It's possible that there are more than three hidden ones total, and that I discovered other ones already without knowing it; I only know that I have two remaining.
So, without spoiling them directly (unless you use spoiler tags), I would like to know if the rest of the hidden achievements are attainable during the endgame scenario, which I define as follows:
Seven masks collected. All wizard attire collected (knotted string, dagger, buckler, glove, cloak, and bracelet). All seven masks put into mirror. Flask of ink collected. Shred of black mask collected.
You can put the actual achievements in spoiler tags if you like, but I'm really just looking for a "yes" or "no" as to whether I can get the hidden achievements from this state. If "no", and you can give me clues as to how early I need to backtrack without spoiling the achievements entirely, that would be excellent as well.