The core aspect that players play DnD for has changed since the early days, while I myself am relatively new participant in the hobby in the grand scheme of things(My first real foray was with the 5e starter set) what I’ve gleaned from discussions is that the focus has shifted from dungeon delving as the core of the game to conquer the challenges presented within, where your character was more a faceless avatar for the player to interact through, to more modern playstyles where it’s more about telling/discovering the story of the characters you’ve created (not a criticism just an observation.)
Dungeons in the old games were sprawling labyrinths filled with traps, monsters and enemies, magic, puzzles, secrets and a whole host of other obstacles and megadungeons were the biggest baddest ones of them all where you could explore for months and still not discover everything it had to reveal, only coming out from underground for more supplies, offload the piles of gold that you couldn’t carry any more of or training your new character levels as that was a thing back then.
But my point is this: could megadungeons be made into viable environments for the current more character-focused playerbase, is it possible to synergise the two gameplay styles when the map only expands down instead of out and caverns and corridors are 90% of what you see instead of the horizons of forests, mountains, giant cities and frozen tundras? A game where you know you’re going to be coming back through these places over and over so instead of just casting flight on the party to cross that ravine you hire carpenters to build a sturdy retractable bridge, set up a protected outpost as a safe retreat in the monster infested halls and build a rapport with the inhabitants of the dungeon town every time you pass by? Do you mug that wandering salesman for all they’ve got or point them towards the corpses of your latest encounter saying they’re free to salvage anything of interest to them?
So I’d like to hear your thoughts on the viability of megadungeons as the setting of modern games, is it possible? Do you like the idea? How would you implement it in your own game?
Can it be done? Yes
I'd go so far as to say that Ptolus was built around the idea.
I did something similar with a home game, by leaned even further into the dungeon delving aspect. The campaign was a location-based campaign, taking place in a city built around a megadungeon.
In fact, the reason for the city existing was because of the dungeon. I loosely based the town on old gold rush towns, with delving for loot being the rush. Stories spread about the mass of riches possible for those willing to brave the dangers. Shops, inns, and other such businesses were built nearby to serve (and make money off of) delvers.
How character-driven play mixed into that is that the stories became about why someone would choose to come there. Sure, there were promises of riches and glory, but -to the average person- going into a danger-filled pit in the ground seemed somewhere between suicidal and psychotic.
•For one character, the story was coming from an impoverished family and trying to make enough (and survive) to save the family farm back home.
•For another, they were tasked by their holy order to retrieve an artifact rumored to be in the megadungeon. The artifact was also sought by a villain because it was believed to be the method through which one could claim a mantle of godhood discarded by a deity long ago.
•For yet another, he was the second born of a noble and viewed unfavorably, so undertaking (and succeeding at) a dangerous quest was his way of proving himself and earning a spot at the family table.
I can't remember the rest right now, but those were two that I remember. Each character had hooks related to why they would choose such a dangerous task or profession. Part of the ongoing story was interpersonal interactions and exploring what was meaningful to each character. Some of it was also the war-veteran-like bond which develops among a group routinely subjected to near-death. In some cases, the dungeon itself revealed information which changed a character's worldview.
I should also point out that a big part of it the diet also involved the outside world not being static. In the case of the character working for the holy order, that meant that other delving teams might be hired (by the opposition) to retrieve the artifact first -which could mean dire consequences.
For the player looking to save the family farm, it meant sending supplies (and money) back home, as well as tuneup family's situation getting better or worse.
I'm not sure if any of this makes much sense, but the point is that it's possible.