Dungeon Maker is sorta the Japanese take on the Western loot-grind RPG (a la Diablo). But it also has you actually build the dungeon for yourself, because what the hell, why not. Even nine years after its release there's still nothing much like it on the market ... the closest analogue that I know of is Chaos Seed for the SNES, which was a Japan-only release but does have a good fan translation. This game doesn't have the breadth of features that Chaos Seed
does, but it's also nowhere near as difficult or confusing.
So you're some sort of entrepreneur who has decided to build a dungeon in a location that seems worrisomely close to the town walls, for the purpose of luring monsters and then killing them for their loots. Since this is medieval times, there are no environmentalists or PETA to get up your ass about it, I guess.
Anyway, you start out just digging out dirt tunnels and rudimentary rooms. But that only attracts methhead bat and wildcat squatters. To get the upper-income monsters, you gotta gentrify the place up with wood paneling, stone corridors, lavish bedrooms, treasure rooms, etc. Then apparently you start getting good reviews on Monster Yelp or something, your dungeon rating goes up and a better caliber of monster moves in and jacks up the housing prices.
You fund all this by killing monsters for their loot, of course. You sometimes get a little money directly from killing them, but much more of your income comes from selling loot that they drop, thus giving the game the Diablo sort of vibe. The game is divided up into days that begin with you in town doing whatever errands you need to, then you get one trip (of unlimited time) out to the dungeon to kill stuff for loot and make expansions/improvements, then its back to town at sundown for any more errands you want to do before hitting the sack.
Interestingly, you don't get EXP for killing the monsters or level up in any way. Stats improve through a rudimentary cooking system instead. Each night you can prepare one meal using ingredients you find/buy and whatever recipes you have on hand. These meals grant a small upgrade to various stats. You also level up some of your equipment by feeding it items that monsters drop.
At first, the game really isn't very engaging. You're just kinda arbitrarily digging out tunnels and rooms without any real strategy, and money for dungeon upgrades is hard to come by. If you stick with it it does start to get some of that addictive dungeon-loot appeal, however. Townspeople eventually start giving you quests and better direction as to how to build the dungeon out. And once you've filled out about half the first level of your dungeon and gotten a couple of carrying capacity upgrades from the poncy museum curator, you'll be rolling in loot.
On the whole the game still is a little too repetitive, though, as the Diablo-esque game tends to be. The dungeon building aspect leavens that a little bit, but not as much as it could. The samey pattern each game day of running through all your corridors, busting in on freaky monster orgies in your bedroom and collecting loot gets kinda old kinda fast. There isn't much to interrupt it besides building a new floor, as each floor brings new quests and a boss monster or two that you can lure. There's no real ongoing story other than wooing the Princess with your redneck monster-baiting, and your main character is as flat and uninteresting as can be.
Aside from the general tedium inherent to the design, the combat is also pretty graceless and clunky and could have used more refinement. An actual town instead of just a rudimentary menu system with static talking heads also probably would have done a lot for the game. As it is, it's still a good concept executed at least decently, but you wish a number of aspects of it would be better. The series did have a few sequels, though, so maybe those did better with the idea.