There’s not a great deal of descriptive language in 1968’s Do Androids Dream of Electronic Sheep (which would become better known as Blade Runner once the film was made). In the opening scenes we’re on the roof top of an apartment block where the tenants tend to their gardens and – most importantly – their livestock, electric or not. The surrounding buildings weren’t really described, but imagination fills in the blanks with run down, abandoned high rises. It helps that we all know the dystopian genre of the book going into it making it easy to summon up descriptions we’ve seen from other books and films.
For the DM, leaning into genre like this means you can focus more on your story than room-by-room descriptions. Setting your campaign in the Underdark does a few things which homebrewing your own world fails at: veteran players already know a lot of history that the Underdark brings, as well as letting everyone know you’re in a fungus coated cave system the size of a continent. This isn’t just for brevity (and the fact that you’ll probably run out of synonyms for “mushroomy”) but the less you describe the more freedom comfortable players have with adding to the scene. Setting the scene doesn’t require a full inventory of a room and doing so means their imagination is limited. You should be able to say “yes” whenever someone asks, “is there a sconce I can take?” They’ll do cool things with that sconce.
The fact of the matter is that our brains do a good job at filling up the spaces which narrators leave for us. This is likely why nerds who with vast amounts of cultural references to pull from enjoy D&D so much. What we need help with is filling that world with function. As the DM, in your prep time, you should be thinking about the impact of your plotline on the world. Philip K. Dick spends most of his book on this: what if there are drones? Smart drones – smart enough to do their job creatively. Well, these drones won’t want to keep working if they had a choice. So, there would have to be bounty hunters who seek out these escapees. Since these drones are so well camouflaged as real, red-blooded humans, the hunters will need a way of sussing them out. Some sort of weakness. Maybe they struggle with comprehending the full range of human emotions. In a world full of suspicion, actual humans would want to show off their emotional aptitude. Taking loving care of an animal would do that.
So, a trait of all humans is that they want to have an animal to take care of and advertise. In a world where most animals are extinct, that makes a curious market appear…
Following this one quirk of the story fills of a society of nameless NPCs to life. Maybe there’s a curiosity of society that comes from a conceit of your campaign. Are devils slowly infiltrating all levels of government? That must have an impact on something – certain rules getting laxer in places where a devil really wouldn’t care. Temples defunded, just enough to notice. Follow the premise of your campaign to its natural, societal conclusion. You’ll be building a much more tailored world to your story. As an added bonus, your group will be constantly reminded of their current quest which some players are in dire need of…
Adventure prompt: Sputput, the most famous gnome tinkering in this neck of the woods, has been produced a shocking number of Whizzbangs, Tidbits, and Doohickies. Until one day his factory goes quiet and nothing comes out. As the characters venture inside to find out what’s happen to the well-loved inventor, they discover his collection of unlawful clones have taken over the shop. It’s time for the adventurers to save the day, but which of the identical Sputputs are they supposed to be saving..?