From publisher blurb:
The old empire of Tuje committed many foolish acts in their search for power, and one of them was to dig so deep they tore a hole in reality. Now, a thousand years later, a strange elevator-like device has been discovered above an apparently bottomless borehole. One expedition went down, and the elevator returned, empty. Now it is up to you to find out what happened, rescue any survivors, and uncover the secrets of this strange site.
In this combat-optional, system-agnostic fantasy adventure, delve into a weird and unearthly realm, uncover its secrets, and find out what kind of a person you really are.
Content warning: mind control, claustrophobia, death.
What sort of system to use?
You don't need much other than some kind of mechanism for resolving outcomes based on players' abilities. It was playtested using a very minimal system we made up on the spot. The decisions the players make are most important.
It's assumed magic exists, technology is limited, and little is known of what happens if you dig too deep underground. It could work for many popular and unpopular fantasy adventure systems, so long as your table likes character-driven stories, and could probably work with many modern or sci fi games, with some adaptation.
There is the opportunity to add combat, but if it combat occurs, you will need to select appropriate monsters for your game system. It is not a major focus of the adventure.
This game lasts about one session, but could be added to a larger dungeon complex or other area to explore.