Rise Up Comus: Metroidvanias and Megadungeons

Sometimes, I see the question: "How do I run an RPG like a metroidvania/like Hollow Knight/like Blasphemous?"

I'm making this blog post mostly so I have something to link to when I encounter it.

Definitions of terms

What is man? A miserable little pile of interconnected, gated dungeons.

"Metroidvania is a subgenre of video games focused on guided non-linearity and utility-gated exploration. The term, popularized by video game critic Jeremy Parish, is a portmanteau of Metroid and Castlevania." - Definition from the sidebar of reddit.com/r/metroidvania

"Some common characteristics and philosophies for a mythic underworld or megadungeon (keep these in mind when creating your dungeon):

1. It's big, and has many levels; in fact, it may be endless

2. It follows its own ecological and physical rules

3. It is not static; the inhabitants and even the layout may grow or change over time

4. It is not linear; there are many possible paths and interconnections

5. There are many ways to move up and down through the levels

6. Its purpose is mysterious or shrouded in legend

7. It's inimical to those exploring it

8. Deeper or farther levels are more dangerous

9. It's a (the?) central feature of the campaign"

- James Cone, Philotomy's Musings

Locks and keys

To open the door, you must do what needs to be done.

The basic gimmick of any metroidvania is that players can see pathways that they don't yet know how to access. This is done through a series of locks and keys.

Locks are anything that prevent the players from making progress.

They can be spatial—something is separated from you by distance
They can be physical—something can physically block your progress
They can be temporal—something only happens at a specific time or after time is spent on a task
They can be environmental—you need to overcome the limitations of the human body
They can be interpersonal—you must convince the NPC that you’re worth helping

The simplest example of this is a locked room. You must find the key to enter it.

But the principle applies to much more than that.

Entire sections of the dungeon can be locked. Example: You cannot journey through the Drowned Marshes without waterbreathing.

Non-player characters can be locked. Example: The ghost of the nurse will not help you until you give her the skeleton of the fair haired girl buried in the First Graveyard.

Specific items can be locked. Example: You can’t pick up the Communion Bread and Wine until you have first confessed your sins.

Certain events can be locked. Example: The ghost of the baroness only appears in the witching hour.

Achieve a metroidvania effect by using obvious locks and hidden keys.

Gated, non-linear dungeons

The map from one of the metroidvanias that lends the genre its name

As a gamemaster, creating a megadungeon can seem daunting, but it’s really just a series of small, discrete tasks.

Break a megadungeon down to its atomic constituent parts.
Populate it with interesting things.
Connect these levels together.

It’s less making one huge megadungeon and more creating several, smaller dungeons. Each dungeon should be interesting enough to stand on its own. Here's one recipe for stocking a dungeon. Here's another.

That said, because you are creating several dungeons and connecting them together, not every dungeon has to have everything. Each dungeon's theme will be reflected by the choices you make while stocking it. One dungeon could be completely devoid of enemies but be full of traps (like Hollow Knight's Path of Pain). One dungeon could be free of both traps and enemies--a rare moment of quiet and place to rest in the center of the megadungeon; a camp between the over world and mythic underworld.

Create locks between these constituent dungeons. Place their keys in places that clever PCs can find them.

One powerful technique is to show the players they haven't unlocked yet right off the bat. Many metroidvanias do this in the first stage to establish the pattern of explore -> find a roadblock -> explore some more -> return to bypass roadblock.

This is what Sersa Victory calls a "Foreshadowing Loop"

Another powerful technique is to show a key behind a difficult puzzle that can be ignored -> the lock that blocks the PCs' progress that contains a clue for the puzzle. This lets players muse over the puzzle in context. See the puzzle, see the blocker, get a clue, backtrack to the puzzle itself.

The non-linearity of the maps and expanse of content works to your advantage. Because there are many ways to go, you can afford to get "stuck" on a puzzle. In linear dungeons, a puzzle that blocks the way forward can cause hours of frustration for player and GM alike. In non-linear dungeons, it's not a problem. The players can leave and continue to play and explore. If someone has an insight or if a key is later discovered that fits that puzzle's lock, they can return. Also, because of the nature of the medium, there should be many ways to solve any puzzle. You're not just trying to guess what the game wants you to do--you're finding logical solutions that work within the context of the game world.

"Story" and level design work together

As you play Hollow Knight, the bright Infection spreads.

In many RPGs, and especially in games of this format, the "story" is what happens at the gaming table. To support this, GMs should imbue the megadungeon with lore seeds that bloom when cared for.

That is to say, do not create a plot--explicit things that you think are going to happen or actions the PCs will take. Instead, create the backstory of the different dungeon levels/overall megadungeon, and let that shine through your choices of traps, monsters, treasures, and special areas.

Embed lore and information into each level. A trap can reflect the theme of what it guards or its maker. Treasure might depict the scene of a historical or recent event. The gold might be minted with the faces of ancient goddesses. Ruins might have partial Rosetta Stones that allow the translation of unknown and forgotten languages. Let your lore shine in dark places.

Ultimately, players might ignore all this as just a bit of flavor. And that’s okay—the game is ultimately about the player’s choices. But, at the same time, if you repeatedly hit your players over the head with bits of lore, they’ll begin to form connections. Things that seemed like one-off bits of description will suddenly be remembered. Players will have “aha” moments. They’ll feel like Sherlock Holmes—and that’s fun for everybody.

Ability-based exploration

In Blasphemous, you upgrade your thorn-covered sword, Mea Culpa, by finding new altars.

Sometimes its okay having the blue dungeon gated behind the blue door which is opened with the blue key. But a key feature of metroidvanias is to unlock progress through ability-based exploration: Samus learns how to drop bombs so that her morph ball bounces up into the tunnel, Alucard learns how to become a mist to phase through gates. It's more interesting to open new levels because the PCs gained a new ability that opened up a new mode of play for them.

There are some abilities that work better in a dungeon-crawling context and some that work less well. The same is true for metroidvania-esque exploration.

Abilities that are bad for metroidvania-megadungeons

In every old-school module, especially tournament dungeons, there was a big list of spells that just didn't work. There's a reason for that.

Passwall: Avoid any ability that removes the essential structure of locks and keys from the dungeon. Passwall (and equivalent abilities) is like that glitch where you pressed Start during screen transitions in Legend of Zelda: Link's Awakening--you bypass sections of the dungeon, but you're breaking the experience.

Jumps and spider climbs: It feels counter-intuitive. Getting a double jump works so well in video games! But TTRPGs have different modes of input than video games. When the GM says: "Ha ha, you cannot reach the door on the ledge because it is, like, 15' up," the players are well within their rights to say "Oh, uh, okay we just climb the wall" or "We have a grapple" or whatever. Putting your next level on a super slick unclimbable wall just feels cheap.

(Although, having written this, I just got an idea for an entirely upside down dungeon that's only really navigable if everybody has spider climb. Although I think you'd get a nose bleed after a few minutes. I guess my point still stands.)

Flight: I'm not an advocate for flight in dungeon crawling games. Too many great puzzles and environments only have tension because the players can't fly right over them. Putting a dungeon in the sky and then giving your player's flight is cool, but comes with a cost. It's better to unlock the sky dungeon through taming a friendly roc or climbing a giant's fishing line.

Teleportation: Teleportation between set points is fine. But the ability to teleport small distances (i.e., through doors) will disrupt the most essential locks (doors) in a megadungeon. Intangibility has the same problem.

Abilities that are good for metroidvania-megadungeons

Giant size / giant strength: Moving huge boulders blocking a door is a classic. It's even better if you have to move something that's inhumanly heavy: cranking a giant winch, pushing open a giant door, winning an arm wrestling contest with a giant, etc.

Tiny size: Alice in Wonderland style, shrinking into a mouse size lets you enter through small doors or navigate doll house dungeons.

New languages: New languages can allow you to traverse the dungeon in dramatically new ways. It might turn enemies into friends--once you can speak to the kobolds, you can negotiate passage through their territory. It might allow you to solve previously unsolvable problems ("Speak FRIEND and enter? We had this all wrong.")

Healing: Sections of the dungeon can be gated by dangers that you can eventually mitigate. For example, you can only survive the Poison Swamp once you gain the ability to Remove Poison. Or a particular type of healing might be needed to bypass a lock: a door can only be opened if the demonic sword pinning it shut has Remove Curse cast on it.

Damage immunity: Relatedly, some dungeons can be gated by hazardous environments. Entering the Dragonfire Forge deals 1 damage by heat every turn. If the players gain Rings of Resist Fire, they can traverse this environment. Or perhaps they can enter the Poison Swamp if everybody gets a gas mask.

Elemental damage: Even without 5E style damage types, puzzles that deal with different types of elemental effects "read" well at the table. To open the door encased in ice, you need to cast a fire spell. To charge up the elevator that takes you to a new level, you need to cast lightning bolt on it.

Water breathing: Water is a great, natural barrier. Water breathing allows you to descend to dungeon levels at the bottom of a lake or traverse the underground river.