A friend and I are in the process of making a roguelike (or rogue-like or roguealike or rogue-lite or whatever. Screw the Berlin interpretation!). I won't tell too much about the greater concept yet but let's talk about some general ideas and design decisions regarding the game.
Our game, which is barely playable right now (it does generate a cave and one can wander around in it and even pick stuff up but there is little to no adversity as of yet - dehydration is currently the only true enemy), has a simple premise: You are a person, assumedly in some medieval time, walking through the forrest/mountain at night when you fall into a hole that is the entrance to a cave-system. You need to find a way out. When you think about it, this can be a rather terrifying thought and I had the idea when visiting a cave on vacation over New Year's 2011/2012. That particular cave was discovered by a man named Baumann (after whom the cave was susequently named) who was a miner in the olden days and got lost in it after his light went out. After three days he managed to find an exit (and tell his tale) only to die of being half-starved and being lost in a cold cave for days. This, I thought, could be made into quite the game. And then I decided to add monsters and some low-key magic. So what about those monsters?
Monsters must be in line with the setting. I didn't want goblins and orcs running around my central-German medieval cave. I wanted things forgotten by the modern world, things that almost made sense. The first monster we are implementing is an oversized rat. I know, it sounds cliché but remember, this is not a sewer. As I like my roguelikes difficult, even this weakest of foes can kill an unprepared player character, although the chance isn't that great for the little critter.
As the game is based around randomizing charts (I can easily roll some dice and generate a floor of the cave or indeed the entire cave on paper), I decided to keep things in low numbers that are easy to keep track of. The player character starts with three hit points and said giant rat (rat-hound, as we call it in-game) has only one. The rat-hound may be the weakest monster in the game but it is also the first tier of the monster class we call a seeker. Seekers are monsters that know where the player is and move in on them until they find them. As the player's visual range is basically limited to the tile they're on and hearing things from neighboring tiles, a seeker has an information advantage over the player.
The cave as a setting is the natural dungeon - and it is for a reason. The wilderness of the area that inspired me to make the game is still somewhat wild to this day, which is something that you don't get much in Germany. This is, of course due to it being a mountainous area, which doesn't really allow for agricultural revolutions or large-scale urbanization. So a couple of centuries ago, this was as remote as you'd get, mountains covered in dark conifer-forrests, the Blocksberg, alleged meeting-spot for witches somewhere here, as well as the Brocken, highes peak of the area, where giants were supposed to reside. Imagine being there. Now imagine that you fall into the mountain itself. At the time there were stories of miners getting lost underground, one of them making a pact with a spirit of the mountain and emerging three centuries later, only to die of age after reaching his home-village generations after everyone he had known had died. Caves are still a place of mystery. Even in a fully explored cave you get the feeling that it must run deeper, there must be a whole world you can't see beyond the light you brought with you. A world where eyeless olms live in subterranean lakes and rivers, their slow metabolism making them immortal. A world where you may find the bones of long-dead cave-bears, cave insects that can never see the sunlight crawling in between them. And maybe, just maybe, there are monsters there And that is the setting to the game I'm making.