Want to build an RPG type game without worrying too much story?
A massive, massive multi-level dungeon, huge number of fetch quests, object puzzles, and wandering monsters?
I think I've got a silly idea you might like.

Lost Property: An Excuse for Arbitrarily Many Fetch Quests

Basically, an excuse plot for RPG fans who like random battles, dungeon exploration, and especially fetch quests.

The idea is that there is an existential lost property office, that has been collecting the stuff left behind in doomed timelines for thousands of years of human history. Some of it is categorised in different rooms (or even floors) based on era, genre, or type, but there’s still some things that have been put in the wrong place, or are in the warehouse until they can be properly classified. And when something isn’t quite on either side of a boundary line, or fits into multiple categories, there’ll be a few different places it might be found.

The people who work in this office are special people; they’re people from throughout time and space who couldn’t find a job anywhere else. Because seriously, nobody actually wants to work here. And you’re the new recruit.

See, sometimes people come in to claim something they’ve lost. Maybe it’s a personal trinket, or maybe it’s the ultimate weapon that would have saved their world if they’d just found it before the end of time. But basically, there’s a ton of junk here, no two items identical, and there’s people who want it. But ever since some idiot opened Pandora’s Box (item №17, according to the original filing system), the Ultimate Evil has been possessing visitors. If they don’t get what they were looking for quickly, they turn into monsters from whatever genre/era they come from. So now there’s hundreds or thousands of monsters wandering the warehouse. Things only got worse when they started stealing the keys. Now you’re trapped in the front office, with monsters all around, and still new customers coming in in search of something.

You need to go into the few rooms you can reach, fight the monsters, and find the “treasure” from various racks. If you can give a wandering monster the item they were originally after, they’ll head for the exit and not bother you again.

Well, sometimes you might have to escort them out to make sure they don’t die in here and reincarnate without what they came for. But mostly, if you can give them what they need, you don’t need to worry about them any more.

I’m thinking that the wandering monster lists for each room can contaminate each other. Like, if you leave a door open, random encounters from one room’s list start being added to neighbouring spaces. So if you play for long enough, the main office will end up containing all the monsters you’ve encountered; so the ‘easy’ areas gradually get less easy. Maybe some monsters (zombies? lizardmen?) even interbreed to create more powerful versions if left in the same area. And when you give someone their item and get them to the exit, that monster disappears from the whole building. But there might be different groups of the same monster, who want different items.

Every monster can eventually be dismissed by giving them the right thing or things, and every item can be given to somebody. This includes the books, diaries, and other documents that might give you clues about who wants what; and also the armour and weapons. And the keys (make sure to leave the doors open before returning a key to the character who wants it). Everybody wants something.

I can even imagine that parts of the game could be procedurally generated, so you get a different selection of items and different customers want them. You can certainly procedurally generate random dungeon levels, and maybe even key puzzles.

If you give somebody the wrong item, they might just ignore it and you keep it. Or they might take it, and you have a chance of getting it back when you defeat a monster of that type in future. Or after a short time it might be randomly deposited somewhere in the region that monster occupies.

I’m thinking that bosses in this game might drop unique items when you beat them, but then respawn. To finish this game, you have to beat a few particular bosses, get key items off them, use those keys to open specific areas elsewhere in the dungeon, and then get the item the boss really wants. Then when you give them the item they want, they’ll give you “rewards” that turn out to be the five keys to Pandora’s Box. Once you got the box out of the safe, you can close and lock it again, and imprison the ultimate demon in it. And of course, give it to the tutorial character who’s been hanging around the main office waiting for it.

But once ultimate demon is defeated, the monsters turn back into people; the customers they originally were. And many of them die, because they’ve been reincarnating as monsters for hundreds of years. So for 100% completion, you have to beat all the other monsters before dealing with the big bad. And to give them back what they’re wanting, you’ll have to be fighting the final boss with no equipment. Hope you spent plenty of time levelling.

(thinking about potions… obviously some items can be replenished. Duplicatable items might be exempt from the “everything has to be given” rule. Or maybe giving an item removes all duplicates too. Or just stops new ones spawning. There’s a few ways it could be done. One I’m imagining is that there’s a fountain of life that generates potion continuously, but there’s only limited bottles/cups in the game. And of course, there’s someone you have to give the fountain itself to at some point.)

a very excellent concept-excuse-story (lol) for just making a game with the mechanics/features but no "real" story/etc

(though, that's so good writing... just for an excuse of not writing/having a story, you might as well make an even more real story, lol)

one thing I'd like to point out though:

randomized dungeon crawling and etc features/mechanics, by itself, without anything story/etc captivating your interest, gets boring and pointless quickly... for the person playing the game.

P.S.

the syfy (sci-fi/sci-fy: science-fiction / science-fantasy --- I hate the use of the 'ys' .... argh... it's not "cutesy"... it's LAME!) channel had a very similar (1 or a few season) tv series...

ht.tp://www.imdb.com/title/tt1132290/
ht.tps://en.wikipedia.org/wiki/Warehouse_13
ht.tp://www.syfy.com/warehouse13/cast/5 (err, hopefully you can navigate it, the site, better than I can, lol)

so, maybe you might want to check out some of their episodes/shows, to get some ideas from it... hehe :D

I did Wumpus... Same idea... Follow the clues to find the creature..
No story, just a re-do of a text game from 1970...
I got 2 reviews...
5 stars... loved it...
1 star... hated it, no room descriptions, no strategy, can't tell where you are going...
Personally, it did not rate as even a dungeon crawl...
But, for a second quest adventure, not to bad... (Even if it wasn't "my" program)
Wumpus 3.0 had new options, and, if you make the "correct" options selection, it is entirely a different game...
(That was fun to do...)
Warehouse13, loved the show... It's rare that there are any "new" ideas on TV any more...
Even if this one was a re-make of Friday the 13th, the series...
Same idea, track down and retrieve "evil" artifacts...

ya... cable tv channels are dead now (aside from syfy and the educational channels -- though the educational channels haven't had much new content for awhile) ... sighs... it's all online and pay/subscription that has the money to create new content