A pipe disappears through a wall. Somewhere beyond it, a machine starts moving. You haven't found the next room yet, but you already have a question about it.
That is a small thing to build a game around. It is also the kind of thing I want Fathom to be full of: details that make you lean forward, form an idea, and go looking.
Fathom is a party-based science-fantasy RPG in development, with authored environmental puzzles and tactical turn-based combat. The dungeon is central to that mix. It needs to give the party somewhere worth exploring, somewhere that can surprise you without making your observations feel useless.
Rooms witH a reason to exist
When designing a room, I find it useful to ask what happened there before the player arrived. What moved through it? Who needed access to it? What is it connected to? Which part has stopped doing its job?
Those questions give an environment a structure beyond the route to its exit. A maintenance passage can explain how a machine was serviced. A viewing window can establish a destination before you know how to reach it. A damaged section can leave evidence of an event you missed.
The player doesn't need a written answer to every question. The space needs enough coherence for an answer to seem possible.
That leaves room for the impossible. A place can behave strangely and still have habits. You can learn those habits, notice when something breaks them, and use that knowledge. That is much more interesting to me than a room where anything can happen simply because it would look impressive.
A machine witH tHe wrong idea
One chapter currently being developed begins with a practical errand: take a cursed blade to a disposal facility. There are controls to operate and an intake to use. The place has a process. Unfortunately, its idea of what should happen to a perfectly serviceable weapon differs from the party's.
That disagreement creates the journey.
The design explores how visible transport lines, inspection machinery, and working areas could let you follow an object through the facility. Sometimes you might reach it. Sometimes you might find the evidence it left behind. A route can become a question before it becomes a path.
The chapter is still in planning, so its individual rooms and solutions will change. What interests me about the premise is the connection between the party's intention and the building's behavior. You want something simple. The place has other priorities. Understanding it becomes part of getting what you came for.