Every year, your friends hold a Halloween party, and each guest must complete three dares. The Psychomanteum is new: a mirrored chamber, in which you must stay, in darkness, for an hour. That shouldn't be too bad, right? You're a connoisseur of haunted houses and all things Halloween, after all, so nothing should really surprise you.
This game has all the usual trappings of Halloween - pumpkin spice, haunted houses, darkness. This contrasts with the genuine sense of increasing derangement as the PC spends more and more time in the titular box.
Psychomanteum has a strong concept, aided by the background music and sound effects. There were some disambiguation issues, if memory serves, and I didn't know what to make of (Spoiler - click to show)the slate. Psychomanteum leaves its truth deliberately ambiguous, but presented some deliciously creepy possibilities.