CD10 Core: Running a Game

Before you begin thinking about running a game in CD10, there are a few things we must go over. Yes, even if you are an experienced game master. Some of what we go through in this article will seem like obvious points to you, others may seem a bit alien. It all depends on your RPG culture and what previous experience you may have had.

How to read this website

First off, we want to go over how we denote things on this website. The first time a core mechanic is mentioned, that term will be in bold font, after which it will be denoted in italics. So the first time you see Excess, for instance, it's bold, but when you see it later in the article, it will be like this: Excess. CD10 and numbers are always bold. In addition to those rules, you have four kinds of boxes describing different things.


The mechanicsbox will explain in short detail how a particular rule or mechanic works. This is generally a short description on the bare minimums of the rule.


The hintbox will appear occasionally to explain concepts, give advice on how to apply certain rules and how to interpret them. They can also be used to give advice on how to run games, how to think when learning CD10 and good game-running practices.


The flavorbox adds fluff and examples. Usually a companion of the mechanicsbox, this box can show off real-world examples of how rules are used.


The sidebar is usually a glossary of terms and short summaries of the whole article. Sidebars are not used in all articles.

If you're a brand new Keeper (CD10's name for the game master) who has never ran a game before, or even played a TTRPG before, you will likely have the least issues with this article. More experienced Keepers, particularly from more mechanics-heavy and crunchy games, may find themselves somewhat at odds with how CD10 was designed. That doesn't mean what you've done up until now is wrong, or even that you can't do it in CD10, just that we had slightly different idea designing the game.


Finally, don't forget that you can use the navigator (Black box with white stripes in the left margin) to navigate the whole wiki and find whatever you need in a jiffy!

What is a Keeper of the Tales (KT or Keeper)?

In CD10, the "game master", traditionally shortened to "GM" or in some cases "DM" for "Dungeon Master", is called the "Keeper of Tales" or "KT" for short. It describes the job better and avoids the connotation that the Keeper is some kind of master, king or head honcho of the party. While most experienced Keepers have a pretty good idea of what a Keeper is supposed to do, we'll tackle some of the core ideas you need to have in mind when running games in CD10.

The Keeper's job

Sometimes RPGs are described as a game between the Keeper and the players, as if it was a contest. Considering the Keeper is the god of the universe and can do whatever she wants with no restrictions, that likeness would lead to the Keeper "winning" every time.

A roleplaying game is not a contest. The Keeper is not out to defeat the players, nor is the goal for the players to "win" anything. The goal, for everyone involved, is to have a fantastic experience of escapism. The Keeper and the players are in cooperation in this, telling the story together.

Small preamble on theme

Obviously, the feel and theme will heavily depend on what kind of setting you're running your game in. It's been said that you can't run a realistic game in Dungeons and Dragons. We'd argue that is patently false. It is certainly possible and a good Keeper and some clever home-brewing of rules can make it a fantastic experience. In the same vein, it can be said that you can't run an epic story in CD10. To that we say that you can, but it'll take some creative home-brewing and different planning.

So, if the Keeper and players are in cooperation and tell the story together, why is there a Keeper in the first place? For two reasons!

The Storyteller

While freeform storytelling exists, and so does improvised theater, CD10 assumes that the plot being told is the Keeper's creation, and the story being told is the collective story. The difference between "plot" and "story" here is important. The "plot" is what the Keeper comes up with. It encompasses the major story progression, the key figures involved and the place where this story happens. The "story" is what actually happens. Usually, this is only loosely connected to the actual plot, as players have a tendency to veer heavily off the planned path. "Off the rails", so to speak. A good Keeper will not tell players that "you cannot do that" or say "I planned for this to happen" and force the players in a direction they want. If that's what you want to do, write a book. Don't be a Keeper.

Flexibility is important as a Keeper. You are there to facilitate the player's adventure, to provide them laughter, tension, sorrow and excitement. To portray wonderful NPCs and make the most out of your storytelling, creativity and acting abilities. If you do not enjoy any of this, perhaps CD10 is not the system for you. As a Keeper, you are required to adapt your plot to what the players are doing. Your job is to give the players excitement, adversity and adventure on the way to their victory. The players should only fail if they really screw up, or if it serves a narrative purpose. Boromir's death in Lord of the Rings is a great example of a narrative failure. He dies, but he dies redeeming himself of his previous misdeeds, showing himself to have grown to a hero. His death has meaning, impact and narrative purpose. Dying to a random "crit" is without purpose. But we're getting off track!

If you take nothing else from these few paragraphs, remember this: The players should succeed, but you should not pamper them, nor protect them from consequences. Their survival and success should largely be in their hands through actions and choices. Death and failure are absolutely options, but you are not there to defeat them or challenge their dice. You are there to tell your plots, with your players being the heroes to tell the story.

The Abjudicator

Well that's a fancy word, now isn't it? What it means is that in most RPGs, there is a ruleset to dictate things. If you remember the definition of a tabletop RPG by Guy Sclanders as we went over in What is a TTRPG?, this ruleset works both for the Keeper and the players, to keep things orderly.

The Keeper's second job is to manage this ruleset and make judgement calls when things are unclear. Some systems have incredibly detailed rules covering every possible situation. Or well, as many situations as possible at least. Those systems are generally a bit harder to learn but once you know them, they're easy to run as you can rely on the rules to do a lot of the work for you.

CD10 on the other hand expects you, the Keeper, to make a lot of on-the-fly judgement calls and using common sense and your own desire for theme to guide what is prudent and not. CD10 does have rules for most common situations, specifically combat, but it will never tell you what you must do. It is very much up to you as the Keeper to decide how your game is to be ran, as long as you have yours and your players' best interest in mind. Which neatly gets us to the next section.

Running CD10

This first section is primarily aimed at Keepers who have ran other games and specifically rules-heavy games like DnD or even Pathfinder. While Pathfinder in particular offers a huge amount of variety through its intricate mechanics and countless feats, classes and races, CD10 offers that same versatility and variety through a hands-off approach. There are no feats or classes to guide your character creation, but there are also very few boundaries or limits to what you want to do.

Understanding the core concept of "If it makes sense for the narrative and doesn't overtly break established mechanics, it should be allowed" is important as a CD10 Keeper. Nowhere in the rules does it explicitly state exactly how far a character can jump, how much they can deadlift, how far they can run etc. Rather than thinking in meters/feet and establishing ahead of time exactly how far a jump is, you should use more vague descriptors when describing a scene. Rather than saying "It's 10 meters across the gap", you could say "To the right of you, there's a building, slightly lower than the rooftop you're on." and not mention the gap at all unless a player specifically asks. "Is it close enough to jump across?" could be answered with "You take a look and as far as you can tell, you'd have to be heavily augmented to make that jump." Or, if you specifically wanted that gap to be described, you offer that description as you're telling them about the rooftop.

Vagueness without confusion

You have to be careful that your vagueness doesn't contribute to the players not understanding the space they're in. CD10 is meant to be played with a Theater of the Mind style, rather than miniatures and battlemaps. That's not to say you can't use these things, but everything about the system assumes you're using TotM for your games. There's nothing stopping you from establishing that a character can jump a total of 3 meters + applicable trait, but that's up to you as a Keeper. The game will not tell you this.


Which, naturally, brings us to the traits system. The CD10 Core: Traits article speaks about how the traits work, but it doesn't really tell you, the Keeper, how you're supposed to handle them in game. There is no easy way to explain or tell you this without being blunt. The bottom line is that there are no rules for how traits are supposed to be used, besides those established in that article or on the traits themselves.

You as the Keeper have to establish for yourself early on what kind of theme and feel you want for your game, because CD10 will generally not tell you when a trait can be used and not. That is entirely up to you. If you want more strict or more loose depends on what kind of game you're trying to run. CD10 is designed with semi-realistic rule-of-cool games in mind, but you can tweak and adjust as you see fit. If you think of 80's action movies you can get sort of an idea of how CD10 is meant to be played. The heroes are heroes but push comes to shove, they're just people. They get hurt and they can absolutely die.

Don't discuss traits during play

The key part to stick to when it comes to traits is to not have discussions during actual play. You make a call and you stand by it. The players have to accept that. If they have misgivings about your calls, let them take that up during the post-session feedback, not during gameplay. CD10 is designed to minimize everything that might bring you out of the immersion and a loud discussion on whether or not a trait should be used is definitely detracting from that.

Determining when a player can use a trait or not has to be your call and you can't rely on anything else than what feels right to you. Can a player use their "Big" trait to help them reach the ladder which is just out of reach? Sure, why not? Can a player use "Loyal" to help boost their hacking attempt? If there's a reasonable reason as to why their loyalty plays in to that particular check, why not allow it?

Making calls for skill checks and setting difficulty

A core tenet of CD10 is that you should never waste someone's time. The ruleset is developed to be quick, out of the way and snappy. In the spirit of this, you should never call for a check if there isn't a narratively significant outcome to the check. Is it virtually impossible for the character to succeed? (Jumping from the ground to an airplane miles up in the air) Is it so easy you don't need to roll at all? (Walking down the stairs). Does it not matter whether they succeed or fail? In all of these cases, calling for a check is a waste of time. The outcome is already set before the check, so the check changes nothing. Make sure all your checks are relevant, offer a challenge to the character and affects the situation and narrative accordingly.

Failing forward

A failure should not be a dead end for a character. The options shouldn't be between absolute success or failure. It should determine whether or not the character successfully perform the action as intended or not.

An example is when a character attempts to sneak past a guard. Failing the check does not mean that they are immediately spotted, but the guard heard or saw something and he's now more alert. Or the character attempts to jump from one rooftop to the next. Instead of falling to the ground (and potential death), a failure means that the character slips and just barely misses the jump. Left hanging on the edge they now need rescue or must climb up on their own, costing potentially valuable time.

Of course, with enough failures, the character is going to get discovered or fall! But even this should not mean death or the end of the adventure. Perhaps they get captured and have to escape. Suddenly, you have a side-adventure on your hands!


With difficulty (DC) you have a scale from 0 to infinity of how hard something is. The guide list in CD10 Core gives you a estimation for how difficult a task is. However, how hard something is also depends on the skill of the character needing to make the check. What does this mean?

In any given party in a game like CD10, you're never going to have all the skills required to cover every situation. There are just too many skills. In more strictly managed games, you may have a core list of 15-20 skills, of which a given party will have a reasonable amount of. Often they also hold some form of base proficiency in said skills, even if they're not trained in them.

For CD10, not having a skill means not having any value in it. You are virtually untrained. This can lead to situations where the Keeper needs a specific skill for a specific situation that has appeared that no one in the party possesses and the outcome of said check will have a narrative effect. In this situation it would be unfair to expect a character with no skill whatsoever to make a DC 9 check.

If there's an "optional" event or knowledge in the campaign, it's perfectly fine to require a normal difficulty check for it, but skill checks should never be a road-block preventing players from progressing. In such a situation, you as the Keeper must be flexible and adjust the challenge as required.

Adjusting DC based on situation

In a situation where a character is put in an unfair challenge by having no skills for what is required of them, you can adjust the DC downwards to accomodate the character. You should never coddle or railroad your players, but giving them fair challenges is more fun than having them roll for something they have virtually no chance of succeeding. You have to be careful and consider when and why you are adjusting the DC.

First consider if skill substitution would be more appropriate and then consider what the outcome means. Can you find another way of letting the players proceed if they fail this check? If so, you should allow the check and make it a reasonable challenge. Otherwise you must find another way of letting the party progress, as a skill check should never be a road block.

Using Skill Substitution

Skill substitution is a powerful tool in both the Keeper's and the players' arsenal. It allows for non-standard and sometimes even completely unrelated skills to be used for a skill check. It can allow a character to leverage their strong skills in situations where they may not be the immediately obvious choice. An extreme example may be a character trying to convince a forensic investigator to be allowed to join an autopsy to find clues. Normally, a Persuasion check would be called for, but the character is extremely skilled in Surgery and may use their knowledge to intellectually convince the forensics expert.

It's a plausible use of skill substitution and the Keeper should be open to players suggesting alternate skill choices for checks. If they make sense and the player can motivate why a skill can be substituted, the Keeper should allow it.

However, the more remote the relation between the skill and the task at hand, the more penalty the Keeper should add. For a very remote skill, a penalty of +3 DC is suitable, while a relatively closely related skill (such as Persuasion to Intimidation) a lower penalty of +1 or +2 is more appropriate.

Adjusting DC based on situation

Keeper: "I'm gonna need you to make a check for Investigation for this."

The Keeper realises as she calls for the check, that if they fail this check, it's going to take a whole lot longer and the adventure will drag. The risk of losing narrative tension and pacing is looming. For this reason, she may adjust the DC down from the standard 9, even if the check technically isn't easy.

Another option is that the player rolls for Investigation and lands on a 7 or 8. The Keeper had initially set the DC to 9, but seeing as the player got close enough and failing would delay the adventure or lose tension, she decides that it's enough to succeed. She may describe it as the player just barely making it or apply some penalty, but still allowing the party to proceed.

If the check has a Status Quo outcome, the Keeper may consider the outcome as such. This allows for failing forward, or allowing progress with a drawback or penalty. In the situation of Investigation, the party may rouse suspicion during their investigation and must now evade capture, or further suspicion, but they have still progressed.

Skill substitution example

In a situation where a character possesses several skills that might apply to a situation, or when they possess a related skill to the task required, skill substitution may be used. In the following example, skill substitution is suggested by the player and the Keeper decides that it is a better call and adjusts the DC accordingly.

Keeper: "Okay, you attempt to follow the creatures into the night. Roll Perception!"

Here, the Keeper decides that while it is night, the creatures are easy enough to follow. So she adjusts the DC to 12 for the check.

Larry: "Can I smell them? I'm a kuna and I have Hound-nose as a trait. Can I use that for this check?"
Keeper: "Sure!"

Larry checks his character sheet and sees that he has Tracking, and that it is higher than his Perception.

Larry: "Actually, we're tying to find them in the dark. Can I use Tracking instead, and still apply Hound-nose?"

The Keeper had not considered this option before, but the substitution makes sense and Tracking is a better choice regardless and changes the DC to 9 for using that skill. The other players, who do not have that skill, still rolls Perception at DC 12.

Running combat

Combat is inevitable in almost every campaign and at every table. It tends to be the most complex thing you can do in a roleplaying game when it comes to rules. This holds true for CD10 as well. However, CD10 is designed to be quick and snappy to run, but not necessarily simple or immediately intuitive.

It will help you to read through the combat rules a couple of times to get a firm grasp of the flow, and only reference it when you need to. But keep in mind that outside of established mechanics, a lot of the abjudication is up to you as the Keeper to "wing it". If you feel comfortable adjusting difficulty numbers on the fly, do it!

The design goal was to make a system that will make combat hectic, fast to resolve and keep the player immersed in the character and situation, rather than becoming a disconnected puppeteer controlling a miniature on a board.

When you are planning your campaign you should avoid planning combat encounters for the sake of having combat encounters, unless your players greatly enjoy playing combat, in which case go right ahead. But ideally, combat should be a procedural experience in your campaign. It should happen because of player actions, not because "you need an encounter this session". If the players are to break into a research facility with gene-spliced, mutated test subjects, you design the facility with guards, workers and test subjects, and ways for your players to accidentally come across any of these.

You have, at that point, not planned a combat encounter, but given the players a playground and a puzzle to solve. If they make choices that take them towards the enemy, or if they mess up hacking, stealth checks or however you want them to be discovered, that's when combat happens. Always through player action, rather than random ambushes on the streets.


I hear you yelling in the back. Don't worry, we'll get to the ambushes right now! Of course the player characters can get ambushed without any input of their own. However, unless you're using combat as a method to break up a lull in action and you can see that your players are becoming tired, uninterested or otherwise not engaged, ambushes should ideally be a result of player action. However, that action can be relatively far in the past, both in terms of in-game time and sessions played. Perhaps the players have something that an opposing faction wants, they have offended or harmed the organization or even an individual and that's why they are now getting ambushed.

As far as possible, avoid having random, non-narratively tied in combat happen to the players. Make each combat encounter tie in to the story or the current area they are in. If they are in a high-crime zone or raider territory, by all means, you can have them be attacked. But a combat encounter should make sense narratively, thematically and it should make sense for the enemy to be in the same place as the players and for the enemy to wish to attack the players.

Random Encounters

This is a matter of taste, personal preference and theme, but random encounters should not be a part of your sessions. Random encounters are designed to deplete player character resources and make a future encounter more challenging. CD10 does not track resources in the same way as more tactically inclined games and does not have hitpoints to deplete. An injury is a significant debilitation to a character that might just cause the party to back off and spend weeks resting rather than continuing the adventure.

For this reason, avoid random and pointless encounters as much as possible. Make encounters matter. Make them personal, if you can. But above all, make them exciting!

Down and out

CD10 has rules for injuries that state that if a character takes a serious injury, they are Down and out, which means they can no longer participate in combat until recovered. This rule should be used for all mooks and mooks should not recover during combat. If the mooks and the combat is especially light, they could even go down from a light injury.

More important enemies and more narratively weighty encounters should have enemies getting down only on serious injuries. But take note that a serious injury is usually not enough to kill a person, or even a beast. Depending on your setting and the lethality of its weapons, a lot of participants in combat may end up injured, rather than killed. Have them surrender, rather than stupidly fight to their deaths. Make the "prisoners" or defeated enemies a liability that the player must deal with.

Do they tie them up and leave them? Do they deliver them to the nearest law-enforcement? Do they murder them? Enemies that are spared could become future allies, or even future nemesies, coming back for vengeance.


CD10 assumes that everyone involved in combat in some way relates to the same average health. Traits can modify this in several ways, but push comes to shove, everyone is going to be roughly equally "sturdy".

If you need an enemy to be much more powerful and able to take a beating from the player's characters, you can add supernatural traits to them, or give them equipment that allows them to sustain through combat. But, ideally, combat should not be a "hit the big thing until it falls down" kinda deal. If you need an epic, super-powerful being defeated, rather have the party perform tasks, either during combat or well in preparation for combat, to weaken the enemy or gather allies to fight the enemy's support.

The end of a campaign in CD10 can be an epic battle against a super-powerful being, but ideally the players should have prepared by bringing items that will weaken the enemy or bring allies to distract the powerful being's guards etc. Avoid having lengthy combat encounters.


Combat is an important storytelling tool and a great way to seed tension and excitement in a session. It must be handled with care and finesse in order to not be pointless or boring. CD10 is not a tactically complex game, so running frequent combats without narrative outcomes is going to bore your players because CD10 is not designed for prolonger or frequent combat.

Non-player characters (NPCs)

Creating NPCs is generally something that should be done in the session planning, rather than during actual play. However, as we all know, it is impossible to plan everything ahead and sometimes players will seek out NPCs or come across NPCs that you did not plan for. CD10 treats NPCs in different levels of plot importance, and the level determines the work you need to put into them. Not every NPC needs a full sheet, list of skills or traits.

It is a good idea to have a list of random NPC names already prepared pre-session. Just a list of random names that you can pick from when you suddenly have to come up with an unplanned NPC on the spot. You can also come up with general short descriptors and even moods to pull from.


The least important NPC is called a vendor. The name is self explanatory. These NPCs are often barely mentioned and are most often people running stores, bars, hotels etc. They're people the players will interact very little with and don't need a huge backstory or even a character sheet. At most, you should quickly come up with a name, their appearance and general demeanor. Their demeanor should be a single word. "Angry", "stressed", "jolly" and "friendly" are such descriptors. It'll help you portray them like people and have something to hold on to.

You can, if you believe the players will spend some time speaking to this NPC, also give them a goal. The goal should be what the NPC was currently doing when the players interrupted them. Were they going to get coffee? Where they going to go get more wares? Where they going to the bathroom? Having a goal set for an NPC gives them more grounding in the world and also helps you portray them since you know what they are currently striving for.


Barely a step up from vendors are the mooks. Mooks are unimportant henchmen meant to be an obstacle to the players either through a social encounter or through combat. Mooks need about as much description as the vendors, but should also have at least one combat skill defined and perhaps a trait or two. Pick only the most prominent traits they possess. You do not have to go into detail. Their appearance can be distilled down to just a sentence, if it's a combat encounter. "The guy with the hat" can be a descriptor.


Goons are the leaders of mooks. Goons have the potential to become a recurring villain or recurring NPC. Goons are stronger, more skilled and more detailed than mooks. If a battle has a goon in it, the goon will be the greatest threat of all the enemy combatants. The goon also stands a greater chance to survive the battle, as goons do not follow the "seriously wounded equals dead" rule that mooks fall under.

Goons should be more fleshed out than mooks. They should have 1-2 combat skills and possibly other relevant skills to their profession, a colorful personality and a handful of traits.

Recurring NPCs

Recurring NPC are NPCs that come back several times in a campaign. They are just as likely to be enemies as they are to be allies. Recurring NPCs require more care and should, ideally, have a full character sheet, a short backstory that you can pull from in conversations with the players and this backstory has the potential to grow as the campaign goes on.

Recurring NPCs do not have to be powerful, but if they are an enemy, they should be more powerful than the players so that they have the capability to be a thorn in the side for the players. The recurring enemy should not directly engage the PCs in combat, but should be present and escape, leading the players closer to victory.


The nemesis is a powerful person or entity that poses as the ultimate bad guy in a campaign. It is usually a person, but it could also be a "monster" or organization. The nemesis is the brains behind the entire plot. They individual, group or entity driving the whole campaign. The nemesis should be your most fleshed out character. A full sheet and a relatively detailed personality description. Ideally you should also go into detail on the nemesis' motivation. Why are they doing what they're doing? What is their goal? What are they trying to achieve? Try to avoid having a nemesis that is "evil for evil's sake". Doing something "because they're evil" is a weak motivation that is highly unsatifying narratively.

Your nemesis doesn't have to be someone who is to be defeated in personal combat. They could be a socially or economically powerful person that has to be stopped and/or brought down by subterfuge or social maneuvering.

Examples of good nemesis'

A good example of a nemesis is Prince Nuada from Hellboy 2. Hellboy does eventually defeat him through personal combat, but as mentioned, it's not necessary for your nemesis. Nuada's motivation is clear, understandable and to a certain degree relatable. A good nemesis is someone who you can understand why they're doing what they're doing and to some point agree with it. Nuada is a perfect example of this.

Any villain that you can relate to in any way and have depth and a clear motivation is a good nemesis.


Experience in CD10 is gained not by completing quests or defeating monsters but by playing the game. The party that participates in a session gets experience depending on what happened in the session. The Keeper can also award additional points to individuals for anything she likes and reward good behaviour in the group. Experience points are spent either in session as hero points or after the session on improving skills or acquiring abilities.

Group points

These are examples of points awarded to the entire group. The Keeper and the group are encouraged to come up with specifics that fit their group. However, progression is designed for between two to five experience points per session so that try and maintain that.

  • Participating: Everyone who attends the session automatically gains one experience point.
  • Clever problem solving: The Keeper may award the group an additional point if they solved a problem in a clever or creative way.
  • Role-playing: The point of playing another character is role-playing that character. If the Keeper believes the group has played as their characters, sometimes even to their detriment, the Keeper can award this point.
  • Positive attitude: If the players have had fun and brought a positive mood to the table, the group gets this point. If someone is having a bad day, don't punish them however.

Individual points

These points are awarded to an individual.

  • Extra funny: Someone may say or do something exceptionally funny. The Keeper may award an additional point for that. Be careful with this one as we don't want to turn our sessions in to competitive stand-up sessions
  • Services: During a long session, people get hungry and thirsty. Someone who helps outside of the game either by cooking/ordering food, drinks and someone who helps clean up afterwards is awarded an additional point.
  • Player's award: Each player is allowed one point to give to someone else, if they want to. The player must motivate why they give this point to this person in particular. There is no bad blood for not giving a point.
  • Teacher: A character who has access to a teacher and studies full time gains one experience point per month. Note that this requires full time studies and thus no adventuring.

Cover image: CD10 Banner by Mizomei


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