N@tO's Need to Know Part 2, Onboarding d20 Fantasy players to Call of Cthulhu/Delta Green

Dire d20 - Mythica DarkIron

One of the questions I see from time to time on the subreddit for Call of Cthulhu and the general roleplaying board, is how can you transition a group from playing a fantasy d20 game like Dungeons and Dragons to a horror/mystery/investigation game like Call of Cthulhu (CoC) or Delta Green (DG)?

Since this has also come up on the Night at the Opera discord, I decided to ask several regular members of the Delta Green community on how to untangle this Gordian knot. They provided the following advice.

The Mechanical Differences

Delta Green was originally an offshoot of Call of Cthulhu, which in turn was based on the Basic Roleplaying (BRP) system.  Explain to your players that this (Delta Green or Call of Cthulhu) is a 1d100 system, where your skills are each a percent value. Player Statistics reflect six core abilities: Strength, Constitution, Dexterity, Intelligence, Power, and Charisma. For normal humans (what players will be playing as), average Statistics fall within the range of 9 to 12. In the case where a player needs to make a test for a Statistic, say for example a Strength test to break a door open, multiply the Statistic score times 5 (in the example, STR x5) to get a numerical value the player must roll under on percentile dice in order to succeed.

In addition to Statistics, there are four Derived Attributes: Hit Points, Willpower Points, Sanity Points, and the Breaking Point.  As implied, these Derived Attributes are dependent on the Statistics of the character.  Hit Points are representation of a character’s physical integrity, a concept all roleplayers already understand. Willpower Points are a mix of a character’s ability to resist mental overexertion and essentially their magic points. 

Sanity Points are different from Willpower Points. Since your players are experienced with d20 fantasy, they may be familiar with the concept of taking psychic damage.  Sanity damage is like psychic damage in D&D, except in CoC/DG a player’s Sanity value ranges from 0 to 99 and it is tracked with its own “health bar”, independent of Hit Points. 

The Unnatural skill, also called the Cthulhu Mythos skill in CoC, acts as a malus to character’s maximum Sanity. The idea is the more a character understands about the true nature of the cosmos (reflected by an increase in Unnatural/Cthulhu Mythos skill), the less maximum Sanity they can have.

A Breaking Point is related to Sanity Points, in that when a character’s Sanity Points reaches the Breaking Point, they gain a mental disorder.  The Breaking Point is then recalculated at that time, to generate a new Breaking Point of a smaller Sanity number.

Rust Cohle, HBO True Detective Season 1

In Delta Green, Bonds are relationships that the character actually cares about and that anchor them into normal human society. Mechanically, Bonds serve as ablative Sanity armor and will mitigate the Sanity damage that players take. They serve as buffers against reaching a Breaking Point.

However, anytime a player burns Bond points to mitigate Sanity damage, they are literally injuring a personal relationship with someone else (usually an NPC) later to save their own mental health now and carry on being rational in order to conclude some mission.

In Delta Green your characters are all doomed, and the slow degradation of their humanity is reflected by their worsening Sanity and Bond scores.

Here are some examples to consider when explaining what Bonds and Sanity damage are to a new group of players:

1. Your character has a shitty and difficult job. They just had a truly unspeakable and awful day. Do they really want to hang out with their family, or ignore their responsibilities and just curl up and go to sleep? 

2. Your character is confronted with some aggressively difficult parenting decisions. But what if they just did not bother? 

3. In True Detective Season 1, Rust and Marty eventually lose all family and friends and then live on their own as they progress through the story. Mechanically this is simulated by the DG bonds system. Bonds give this a simulated number to determine where you are with whom relationship wise. Story wise, characters just get worn down by this job.

4. What does burn out look like to you? 

The Tone: Mystery, Horror, and Investigation

Tone is setting.  Most d20 fantasy settings encourage superheroic characters and story arcs where characters continually improve. 

The mystery, horror and investigation tone of Delta Green is radically different. In Delta Green all the characters are doomed by the narrative. In other games your characters are going to get better over time. In DG they degrade as they get more experienced.

When coming from a heroic fantasy game, change your player’s expectations as to what they should experience in play.  In a Delta Green game player characters will not always win, and if they do not die, they may get worse physically or mentally.

Characters are likely to die based on the design of some of the core mechanics. Combat in DG is not only lethal, but fast and lethal. At any given turn there is a chance that some other character can kill you.  Let us put some numbers on that subject so that you will have an example to point out to players.  The average hit points for a human character range from 10 to 12. A medium pistol that most Law Enforcement Agents carry (and that are easy to acquire in the US for most cultists) does 1d10 damage.  If you are unlucky, one shot from that pistol can kill your character outright.  Also keep in mind that a well-aimed car in Delta Green will absolutely erase your character from existence.

“Treasure” from AD&D Player’s Handbook by David A. Trampier

Having discussed the lethality of the setting, a word about the murderhobo mentality that is sometimes observed among players of d20 fantasy games.  I will define murderhobo behavior as a player attempting to use combat, violence or intimidation on every situation or NPC they are presented with to advance the plot. This activity breaks believability in modern games and damages the tone of mystery, horror, and investigation games.

To deal with this problem, the Night at the Opera hivemind suggested the following points:

1. Remind the player that Delta Green is set in the present day. The setting is the real world and there are real world consequences to actions. As a corollary, if the player shoots an NPC in public, remind them that everyone has a phone. 

2. Most importantly, gently remind the player that the purpose of the game is for the group to have fun, and actions taken by all players (and the Game Master is a player too!) should enhance the fun of the group.  Do not take actions to have fun at expense of other people.

Another consideration about the tone is that players in a horror game should be ready to be vulnerable. Since Delta Green characters are at risk of severe physical and psychological harm, the players need to be open to experiencing and roleplaying those situations and communicate their limits with their fellow players and the Game Master.

One last piece of advice was, since Delta Green usually has elements of mystery and investigation in the tone, players should take notes to keep track of information.  A good idea is to share a Google Doc of notes with all the other players. Whomever is the least-active in the current scene should write down the clues found.

We hope these suggestions help Game Masters smoothly introduce new players to Delta Green and Call of Cthulhu, and help everyone at the table have more fun.

Acknowledgements

I want to thank the following people from the Night at the Opera discord for ideas and review of this post: Bird Bailey, Sammy J, Fee Fi Fo Fin, Frahnk, and magnificentophat.

Update: 6/14/25

Session Zero

5th Edition Dungeon Master's Screen by Hydro74, image by AugusteBlanqui

A Session Zero is a precursor session for a roleplaying group where ground rules are discussed and the GM introduces the tone and objectives of the game or campaign. Generally, this is the session that characters are made with whatever prerequisites are required for the initial adventures.  For example, you might need a healer in the party if you are running a dungeon crawl, or a detective type character if you are running a police procedural investigation.

The Session Zero is not a new concept. As I recall, I was first exposed to the term when I was reading the Dresden Files Fate game around 2010, and some internet research on rpg.net suggests the term was in use as early as 2003.  Back in the AD&D era, an informal version of Session Zero was just called a conversation with the DM. 

In either case, communication of player and GM expectations is the point of the matter. 

In a Delta Green game, a Session Zero is the perfect opportunity to discuss the tone and Game Master expectations with players. Since this is likely their first time with a new system, the GM can introduce the idea of horror and mystery in a game, and what the GM expects of the players; whether it be certain skills needed to not fail at the mechanics of the adventure, or character behavior during the investigation.  This meeting should start everyone on board with a clean slate, with the understanding that they will be playing something different than d20 Fantasy. 

Recommended Beginning Scenarios, Delta Green

Since this blogpost is focused on players and Game Masters new to Delta Green, here are some suggestions for free adventures that are focused on introducing the game to a new group.  The question of “what beginner adventures are right for my group” comes up quite often on the Night at the Opera discord, and everyone has their favorites; these are just some of mine. I will explain the utility of each adventure as I see it after they are introduced. As such some adventure spoilers will be discussed to players, please avert your eyes from this section. 

First and most venerable, I must start by introducing the official scenario Last Things Last.  Much has been written about this adventure around the internet, so I will just say that it is short, introduces investigative work at the beginning in one contained location, gives the players room to breathe and roleplay, and usually introduces combat at the end. Last Things Last is in the free starter rulebook Delta Green: Need to Know.

The Signal Smugglers by mellonbread. A perennial favorite, this scenario does the brilliant thing of having the players smash cut to roleplay police (who are not their characters) outside of an apartment. Combat is introduced and chaos ensues. However, since this combat is an introductory scene not related to the players’ actual characters, the GM can introduce the fast and lethal combat of Delta Green without consequences for the player characters. After the initial sequence, an investigation is introduced with antagonists that can actually be negotiated with.  

Enemy of the Tribes by David Tormsen.  This was the first adventure I played in, in my current DG campaign.  I have written a partial after-action report about the experience here. The adventure starts out with a crime scene and then blossoms out to a more general investigation and tracking down of other potential victims.  The monstrous antagonists can be used as combat or eerie encounters at any point during the investigation, and likely make an appearance during the finale.  Some work is required to create combat encounters appropriate for your party of players.

The Button by Will Roy. This adventure is primarily a roleplaying event with some investigation around an enigma that is like intellectual quicksand.  It is a great way to introduce the Mythos as not just unspeakable alien gods and rabid cultists.  There is an option to include a Mythos gribbly at the end if the Game Master desires. 

The Midnight Sun by Will Roy.  This adventure was my first reintroduction to Delta Green after a years long hiatus. It works really well with two players with complementary skill sets. Though in the Delta Green world, this is actually an M-EPIC scenario. M-EPIC is the Canadian mirror to the US Delta Green anti-Unnatural program. For more details about M-EPIC check the Delta Green Handler’s Guide, specifically page 271. 

To make this a Delta Green beginning scenario, simply change the location from the Yukon to somewhere in Alaska.  A Game Master may also need to change the origin of the NPC McBee from an “American” to someone who simply is not familiar with the freezing wilderness far from civilization.  The Mythos gribbly presents an interesting roleplaying experience, sort of similar to the end of Last Things Last (above).   I wrote up a semi-novelized after-action report of my experience with The Midnight Sun,here.  

Take the A-Train by Bird Baliey. A great introductory scenario that can be dropped into a campaign to interrupt a chase scene (the player characters need to take the subway) or played by itself.  Think of this game as a stage play.  It is in one location with a fixed number of characters and a common problem. Great opportunity for roleplaying under increasing tension.

The (Un)Natural Man by Bird Baliey.  A domestic disturbance that leans heavily on investigation, roleplaying and interpersonal skills to deal with adversarial NPCs.  The finale may involve conflict with a Mythos gribbly or may be very dark. If the Game Master has a streak of dark humor, this is the scenario to play to exercise that inclination.  

Five Alarm Firefight by Bird Baliey. A Delta Green adventure designed to introduce new players to the nuances, dangers, and mechanics of combat as well as rules like exhaustion. Puts the players into civilian law enforcement or rescue roles with no prior knowledge of the occult needed. They will get plenty of that if they survive. This scenario is most analogous to a dungeon crawl because the player characters will investigate an apartment building room by room with investigative skills to attempt to find clues, and interpersonal skills to deal with NPCs. Ultimately both tactics will be fruitful for unraveling the mystery.

Having said that, the structure of the adventure is not a linear railroad. There are multiple instances where there are alternate routes to take, even if they all end in a central fixed climactic scene. The danger from humans with firearms will be on display.  Pregenerated characters are included for the adventure.

My understanding is that Five Alarm Firefight will be updated soon, so check the link on occasion!

Recommended Beginning Scenarios, Call of Cthulhu

I was originally the always-GM for my Call of Cthulhu group in the late 90s. I have not kept up with the plethora of adventures for the system, but I do remember the classic adventure The Haunting. And I remember it fondly because one of my investigator players never made it up the basement stairs under his own power. Thanks to a Series of Unfortunate Events (just read The Haunting, seriously), his companion had to drag his physically knocked out ass upstairs twice to save his life.  Good times were had by all. 

The Haunting provides a series of floating encounters that can be plugged into the adventure at the GM’s discretion.  It is a classic for a reason and many others have opined far better than myself all over the internet. 

The Author by MrNightmares. I would be remiss if I did not shill my own Call of Cthulhu adventure.  Made for one or two players at maximum, the adventure features a mysterious disappearance and a timeline of events that ratchets up the tension as things get worse until there is a potentially fatal endgame if the players do not put the clues together in time. The weakness in this adventure is that it can hinge on the players finding and reciting a certain incantation to get the antagonist’s attention, so Game Masters may need to work on that.   Features one antagonist that may not be all that terrifying to confront depending on how the players proceed.  Could link this adventure into further adventures against a Cthulhu cult. 

Afterword

Want more adventure recommendations or just more advice on how to start playing Delta Green? Check out Sammy J’s Beginner’s Guide here.  It is worth your time.