4 Hours w/RSD - Introducing Undermountain (Ryan Dancey)

The past six columns I’ve been laying the groundwork to talk about my own personal home game and why I think it will be interesting to the people reading this column.

I haven’t played in a tabletop RPG group since I stopped living full time in the Seattle area about 10 years ago. During the time I’ve been gone I’ve played a handful of pickup one-shot games and played in several convention games but haven’t had a regular scheduled gaming night. That’s changing this week.


I’ve spent the past week or so creating my home game system that I call “Undermountain”. Actually it would be more fair to say I spent a week writing down the ideas I’ve had about how I’d like my game to work – most of the mental labor has been done in idle moments over the past several years.

The pitch is simple: Your characters are members of a unique adventurer’s guild / inn / general store that has an artifact that lets parties be transported into a virtually infinite underground environment (The Ruins of Undermountain) filled with puzzles, monsters, traps, and loot.

It happens to be set in the big fantasy city of Absalom on Golarion, the home of the Pathfinder tabletop RPG, but you won’t be spending much (if any) time in the city. The game is focused on dungeon crawling. It is designed to do some very specific things, all related to packing more fun into our 4-hour game session.

  • The game is derived from Pathfinder, which I consider the most robust implementation of the kind of game I want to play.
  • The game is designed to be quick and easy for new players to understand and for people who have played any version of D&D or AD&D to be able to grasp very quickly.
  • The game is built around the Open Game Table philosophy of encouraging drop in players, people who attend irregularly, and newbies unsure about this whole tabletop RPG thing as well as regular players who expect to play every week.
  • It is a testbed for ideas I’m working on for my current project in the MMO space where I earn my living these days. I can prototype and test concepts that I might want to explore more fully in the digital realm without having to worry about the complexities of getting software and graphic assets actually created to my specifications.

Let me discuss each of these things in detail.

Derived from Pathfinder

It would be fair to say that Undermountain is to Pathfinder what Chess is to Advanced Squad Leader. The more complex game is designed around the idea that highly experienced people willing to invest tremendous amounts of time can create a unique and special experience that is detailed, realistic, packed with choices, and customizable to a wide range of scenarios.

Like Chess, Undermountain is a much simpler game that tries to do just a few things but do them very well, while providing an environment that is “easy to learn, hard to master” – or rather “easy to learn, rewarding to master”.

The design goals for Undermountain were as follows:

  • Standard Pathfinder character archetypes
  • Standard D20 3.x mechanics
  • A focus on “dungeon” style adventures
  • Limits to character movement and knowledge
  • Characters who could solo but work in more interesting ways in groups
  • Easy access to D20 support content (monsters, spells & magic items most significantly)

The Pathfinder core rulebook is 576 pages. It includes essentially everything you need to play a highly detailed, very complicated, extremely well tested game from the day a character is created as a 1st level nobody through to that character being a 20th level demigod plane-traveling Übermensch. You get spells, magic items, classes, prestige classes, and encyclopedic lists of Feats. The only thing you don’t get is a catalog of monsters; but never fear, Paizo provides you with not one, not two, but soon to be three huge collections of monstrous creatures for your game. If you put all the Pathfinder core books together, you’re looking at something like 2,000 pages of content (to say nothing of the extensive line of Golarion Campaign support material and Pathfinder Society scenarios).

Undermountain does not exist as a printed book. It is designed to live as a wiki, a hypertext, user editable document hosted on a website. Wikis do have pages, and Undermountain currently clocks in at 46 pages. Some of which contain about a paragraph of text. And it (like the Pathfinder Core Rulebook) doesn’t yet have any monsters in it.

It cannot possibly do what Pathfinder does, but what it can do is create a hugely fun experience based around moderately powerful player characters exploring a dungeon, fighting monsters, solving puzzles, exploring, gaining phat loot, and powering up.

Undermountain doesn’t have to contain all those pages of data and rules because it can simplify a Pathfinder rule, and then link to the Pathfinder source in the event that the simplified version of the rule needs help. I don’t expect to have to consult the game’s “Big Brother” very often, but knowing that we can removes a lot of concerns about the robustness of the game system.

Since Pathfinder iterates on the D&D 3.0 and 3.5 game systems, it provides a lot of very well tested basic mechanics that are easily leveraged. When you strip out the special cases and just use the core rules systems, you get something that is fairly lightweight and easy to understand. I didn’t have to invent bonus types, or conditions, or any of a myriad of other things that my game needs – I just use them as Pathfinder uses them, just with less text.

Quick And Easy To Understand

There’s really good research that shows that humans actually gain less enjoyment from having lots of choices than from having fewer. D20 gave players so many choices that it overwhelms many people. They just can’t figure out where to start or what tradeoffs they’re making, or how to get all the materials put together in a way that gives them the kind of experience they want.

Undermountain tries to avoid this problem by giving people very streamlined choices.

Character Creation

When you create a character, you pick a race, an alignment, and 5 class levels. Then you do a little bit of customizing of those classes, and then you buy equipment from a very limited list of options.

All of these sub-systems are designed to present very easy to identify choices. You can’t really end up with a bad character unless you purposefully do dumb things (like give a melee fighting character a really bad Strength – and the rules even tell you not to do that and why).

Along the way I cut out a lot of options and choices.

You get a lot fewer choices of race. In fact there are just 5: Humans, Elves, Dwarves, Half-Orcs, and Ophidians. Ophidians are snake-people. They exist for the handful of players who want to play something really alien, and I expect them to be played quite rarely. Racial choices do just two things: They give you one bonus to an ability and one penalty to an ability; and they give you a simple racial power.

I really altered the alignment system. Instead of a logical two axis system like that in D20, I provide the players with arbitrary alignments appropriate to a dungeon crawling campaign derived from my observation of hundreds of players over dozens of years. In Undermountain, your alignment choices are Good, Chaotic, Scoundrel, and Badass. I probably don’t even need to explain what those mean. (There are additional NPC and monster alignments: Evil, Alien, Domination, Hive and None).

You can’t play a Bard, Barbarian or a Druid in Undermountain. There is no Monk class but there is a simple way to customize the Warrior class to make a Monk character (without 20 levels of individual special powers).

You don’t have to pick skills. You don’t have to pick Feats (but you do get 5 points you can spend on modifying your classes according to a few simple rules and a short list of options).

Other than calculating how much your chosen armor and weapons cost after you enhance them, buying your starting gear is extremely simple.

It takes about 5 minutes for an experienced person to make a character from scratch, and most of that time is spent writing, not making decisions. I expect it will take about 20-30 minutes for someone who has never played a tabletop RPG before, and somewhere in the middle for inexperienced players.


Spells are one of the things that really slows D20 down. The spell lists are so huge and the rules determining who can cast what spells and how often and how they work and how they interact with all sorts of subsystems are incredibly opaque.

Undermountain chops those rules down to nearly nothing. There are two kinds of spells in Undermountain currently – Low Level and Medium Level. They are derived from the 1-3rd level Pathfinder spells and the 4-5th level Pathfinder spells. The only spells in Undermountain are simple, easy to understand effects. You can’t travel through walls, into other planes, or from point to point. You can’t see or hear information unless you’re physically present. You can’t summon other creatures. You can’t modify your own, your companions’ or your opponent’s ability scores.

Each spellcasting class (there are 3) does a very specific thing:

  • Clerics heal and remove negative conditions like sickness (and they are good fighters and can still destroy undead)
  • Sorcerers help control the battlespace and make other characters more effective, and solve problems that can’t be solved by brute force
  • Wizards deliver lots of damage and lots of synergistic effects for melee combat characters

The other thing that is interesting about the Undermountain spell system is how often you cast spells. You cast them a lot. Basically, I want the players playing spellcasters to stop worrying about spells as a resource – just like fighters don’t think about melee attacks as a resource. Between hit points, potions, food, and time, they’ve got enough pressure pushing the adventure forward without asking the players to stop so their characters can sleep every 30 minutes of realtime.

There are 21 low level Cleric, 20 medium level Cleric, 14 low level Sorcerer, 15 medium level Sorcerer, 10 low level Wizard and 7 medium level Wizard spells. And that’s more than enough to do virtually everything I need spellcasters to do in Undermountain.


The biggest simplification to combat is the removal of Attacks of Opportunity. They’re just gone – nothing replaces them. That’s a huge amount of overhead that was generating very little in the realm of “fun” for most players.

There is also no reach weapon system (there is a weapon that acts like a reach weapon but its ability is codified into its description).

The elimination of the Feat system also massively reduces the complexity of the combat system. It’s reasonably easy for even a new player to figure out what kinds of things he or she could do at any point in a fight, and what the likely best course of action is.

My goal is to take combat down to a level of simplicity where I can give a new player a short 10 minute tutorial, and then they can fight their character without help and do a reasonably good job (not the best possible job, and not the most creative job, but a reasonably effective job).

Leveraging Open Table Gaming

I travel a lot. Many of my gaming friends do too. It has always been a problem in keeping a regularly scheduled game running. The constant changes in character line-ups and the loss of continuity from session to session has frustrated me to no end.

Undermountain is designed to avoid those problems as much as possible.

The Session

Everything begins and ends in one 4-hour session. The characters all start in a place of relative safety. They get a briefing on where they’re going and what they’re going to be rewarded for doing. Then they go into Undermountain to play the game. At the end of the session they emerge (if they haven’t all died).

Most character resources are automatically replenished at the start of each session. Virtually nothing permanently affects characters from session to session except increases in class levels, and the gear they own. Characters level up every 4 game sessions.

Multi-session plots, such as they are, will be broken down into atomic units that can be resolved in one session. Players who have seen other bits of the plot may have a slight advantage, but nobody will be confused about what is happening or what the stakes are.

Characters Are Well Formed

It would be possible to run an Undermountain session with just one PC, or with a very large group. Because each character is basically guaranteed to be serviceable as an explorer and able to defend itself by itself the game won’t break down if a critical character is absent.

Undermountain Is Infinite

Likewise, the area of the session is essentially mutable to match the power and skill of the group who assemble for a session. The challenge level of the game can be configured so that it shouldn’t overwhelm the party, but also gives them plenty of options to wander off and get themselves into huge amounts of trouble.

If the group wants to play an extended session its very easy to keep the game going – there’s so much material already produced for Undermountain that I’ll never likely use it all, and if I wanted to I could easily spin in Monte Cook’s Ptolus, and AEG’s World’s Largest Dungeon too.

Testbed for Ideas

One of the biggest differences with standard D20 that I am testing in the Undermountain game is getting rid of the Will/Reflex/Fort save system. Instead, each ability score has a corresponding Resistance Roll. While this sounds more complicated than D20, I believe that it is actually far less complicated in the long run.

The classic system requires a lot of mental gymnastics if something doesn’t fit into the simple 3-part model. And that means that the game system has lots of special rules and subsystems to deal with the kinds of challenges that don’t fit into that system. Those kinds of rules proliferate and create huge headaches for players and GMs alike.

In Undermountain players and GMs can quickly see what Ability should be used to resolve a test. In fact, I have renamed two of them to make even more clear what they do. Wisdom has become Perception, and Constitution has become Fitness. Using this setup I was able to quickly convert all the spells and magic items from Pathfinder to Undermountain on the fly as I wrote their text into the wiki.

Another thing I’m testing is my injury system.

In Undermountain, you basically only die from a handful of things that usually involve the removal of your physical body from the game (like disintegration or falling into an underground river). When you reach 0 hit points you fall unconscious. You can be revived by getting your negative hit points removed taking you back to at least 1 hit point. And then you take an Injury. These are serious things that affect your character’s ability to act. You can remove them as well if you have help from someone with the proper abilities.

I actually do expect a lot of character death because Undermountain is a really dangerous place. I think the most common form of death will be a Total Party Kill. That’s ok, because making new characters is really quick. On the other hand, I don’t want to bog my game down with corpse runs, resurrection hassles and all the other stuff that typifies your average D20 game after the characters get access to advanced Clerical help. Players who do value their PCs, who have built them up over time, and want to keep advancing them will have an incentive to run away when the danger level becomes too great, and that’s a behavior I’d like to encourage. Hopefully the newbies will see and emulate this, as opposed to the “death is a minor inconvenience” play pattern I witness in many D20 games.

Both of these changes will be very easy to reverse if I don’t like how they work in the game. I see them as incremental improvements not revolutionary change.

Future Updates

The very first Undermountain game will be played this week. I’ll try to post some actual play reports in the comments following this article for those who are interested. I’ll also be writing more about Undermountain in the future, because I want to break down some of the choices I’ve made in more detail and explain the rationale behind them. So look for lots of interesting follow on content in the blogs to come.

--RSD / Atlanta, August 2011
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Ryan S. Dancey

Ryan S. Dancey

OGL Architect


Interesting article. For me, the most interesting parts were your discussion of spellcasters "not treating spells like resources", and the notion that any character should be a viable option for solo play.

However, one thing I've always found difficult with games of this sort is that house rules invariably add complexity to the game as a whole, and that this applies even if those house rules are intended to simplify the game as a whole - since they pretty much require an understanding of the 'base' rule and then of how it is modified. As far as I can see, this can only be escaped if the rules are written in a stand-alone manner, so they don't have to refer back to the 'base' set. So, does the Undermountain wiki provide everything a new player needs to understand to get started, or is there a lot of rules-info reserved for the DM-side, or have you solved this house rule issue in some other way?

Matt James

Game Developer
Are you just copying the Undermountain from the Forgotten Realms and putting it into Golarion?

I really like how you have paired things down. I might try to run a couple of your variant options. I am most interested in the injury system. I've been tinkering with a few and think it can work well depending on the group.
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Interesting post Ryan. Seems like you went the Castles and Crusades kind of system though by stripping down Pathfinder.

Anyways, I look forward to reading how it works out for you!

Happy gaming!


Given all the changes you've made, why did you base it on any sort of D&D game in the first place? I would think that a classless system would have gotten you to where you want to go more quickly.


I am most interested in the injury system. I've been tinkering with a few and think it can work well depending on the group.

I blatantly ripped off Dragon Age. :)

Here's my chart:

Injury Effect
Badly Bruised: Hit Points received from healing magic are halved.

Broken Bone: Cannot use Dexterity Modifier. Vulnerable to Sneak Attacks.

Concussion: Cannot cast spells or use spell-like abilities without making a Concentration skill check vs. DC 20.

Coughing Blood: Character is Fatigued.

Cracked Skull: Cannot use Intelligence Modifier.

Crushed Arm: Cannot fight with two weapons, or with a weapon & shield (choose either a weapon or a shield).

Damaged Eye: -2 injury penalty to Melee Attacks. -6 injury penalty to Ranged Attacks.

Deafened: Character is Deafened.

Gaping Wound: Character's max hit points are reduced by 1/2. Any hit points above that total are temporarily lost.

Head Trauma: Cannot use Perception Modifier.

Open Wound: Bleeding 1d6 hit points per minute.

Torn Jugular: Make an Fitness Resistance Roll vs. DC 20 before taking a Move Action or a Standard Action in combat or be Nauseated for 1 round.

Wrenched Limb: Movement rate reduced to 1/2 normal. Cannot carry a Heavy Load.
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Given all the changes you've made, why did you base it on any sort of D&D game in the first place? I would think that a classless system would have gotten you to where you want to go more quickly.

Removing things is not the same as changing things. The design goals include Pathfinder Archetypes, and people familiar with D&D being able to play with little difficulty.


As far as I can see, this can only be escaped if the rules are written in a stand-alone manner, so they don't have to refer back to the 'base' set. So, does the Undermountain wiki provide everything a new player needs to understand to get started, or is there a lot of rules-info reserved for the DM-side, or have you solved this house rule issue in some other way?

The Undermountain wiki is complete from the player's perspective. It is incomplete from the GM's perspective (at this time) (for example, there's no monsters in it yet).

You don't have to refer to Pathfinder to play Undermountain. But if we get into some corner case situation where there are questions about the best way to rule on something, we can easily look it up in Pathfinder and use that system, rather than the GM having to ad hoc something on the fly.

At its core, Undermountain should be instantly familiar to anyone who has played any 3.x game. You have hit points and armor class, you roll d20s, add modifiers and compare them to DCs to resolve challenges, etc. There's just a lot less of "no you can't do that" (mostly by scoping the game & the character abilities in a way that limits the chances the players will try to do something twisted).

Here's an example of what I mean. In Undermountain, a Sorcerer that can cast a medium level spell could cast this one:

Black Tentacles

Sorcerer creates a circle with a 20 foot radius within 100ft + 10ft./Sorcerer Class Level of the Sorcerer. The area erupts in rubbery black tentacles. Creatures within the area or entering the area are subjected to a Grapple attempt (d20 + Sorcerer Class Levels + 5). Grappled characters take 1d6+4 points of damage each round. The tentacles cannot be damaged but they can be dispelled. The area is considered Difficult Terrain. The effect lasts 1 round per Sorcerer Class Level.

If for some reason we needed more help adjudicating something about this spell, we'd just look up the Black Tentacles spell in the Pathfinder Core Book (or the online Pathfinder SRD: http://www.d20pfsrd.com/magic/all-spells/b/black-tentacles)
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Lord Crimson

This sounds fairly awesome, actually (especially as I've been leaning back towards the dungeon-crawl as my preferred RPG milieu, what with the limited gaming time that seems to accompany personal fiscal responsibilities).

Ryan, will we be given access to the Undermountain wiki at some point so that we can help break... er... I mean try out this latest innovation?

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