Matrix dice rolling bot with support for the Chronicles of Darkness 2E Storytelling System and Call of Cthulhu.
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Tenebrous Dicebot

Build Status

This repository is hosted on Git and mirrored to GitHub.

This is a dice rolling bot for facilitating roleplaying games on the Matrix messaging platform. It currently has basic support for the Chronicles of Darkness 2E Storytelling System and Call of Cthulhu, with plans to extend the codebase further to support other systems and character sheet management.


tenebrous-dicebot is a dice rolling bot for facilitating role-playing games over Matrix (and anything that Matrix can bridge to, like Discord). It currently has the following features:

  • Rolling arbitrary dice expressions (e.g. 1d4, 1d20+5, 1d8+1d6, etc).
  • Rolling dice pools for the Chronicles of Darkness 2E Storytelling System.
  • Rolling dice for the Call of Cthulhu system.
  • Works in encrypted or unencrypted Matrix rooms.
  • Storing variables created by the user.

Building and Installation

Docker Image

The easiest way to run the dice bot is to use the official Docker image. It is distributed on GitHub Container Registry by a CI pipeline.

The latest tag always points to the most recent successfully built master commit and is considered unstable, while individual tags are considered stable.

  • Unstable: docker pull
  • Stable: docker pull

This image is based on Void Linux. To build the image yourself, run docker build -t chronicle-dicebot . in the root of the repository.

After pulling or building the image, see instructions on how to use the Docker image.

Build from Source

Precompiled executables are not yet available. Clone this repository and run cargo install.

Building the project requires:

  • Basic build environment (build-essential on Ubuntu, base-devel on Void and Arch, etc).
  • Rust 1.45.0 or higher.
  • OpenSSL/LibreSSL development headers installed.
  • olm-sys crate dependencies: cmake, libstdc++.
  • glibc.

Why doesn't it build on musl libc?

As far as I can tell, the project doesn't build on musl libc. It certainly doesn't build a static binary out of the box using the rust-musl-builder. This appears to be due to a transitive dependency of the Rust Matrix SDK.

Any PRs to get the project or Matrix SDK to properly be built into a static binary using musl would be very useful.


To use it, you can invite the bot to any room you want, and it will automatically jump in. Then you can simply give a dice expressions for either the Storytelling System or more traditional RPG dice rolls.

The bot supports a !help command for basic help information about its capabilities.

Basic Dice Rolling

The commands !roll and !r can handle arbitrary dice roll expressions.

!roll 4d6
!r 4d7 + 3
!r 3d12 - 5d2 + 3 - 7d3 + 20d20

This system does not yet have the capability to handle things like D&D 5e advantage or disadvantage.

Storytelling System

The commands !pool (or !rp) and !chance are for the Storytelling System, and they use a specific syntax to support the dice system. The simplest version of the command is !pool <num> to roll a pool of the given size using the most common type of roll.

The type of roll can be controlled by adding n, e, or r before the number, for 9-again, 8-again, and rote quality rolls. The number of successes required for an exceptional success can be controlled by s<num>, e.g. s3 to only need 3 successes for an exceptional success. All modifiers should come before the number, with a : colon.


!pool 8      //regular pool of 8 dice
!pool n:8    //roll 8 dice, 9-again
!pool ns3:8  //roll 8 dice, 9-again with only 3 successes for exceptional
!pool rs2:5  //5 dice, rote quality, 2 successes for exceptional

Call of Cthulhu System

The commands !cthRoll, !cthroll, !cthARoll and !cthadv are for the Call of Cthulhu system. !cthRoll and !cthroll are for rolling percentile dice against a target number. A b: or bb: can be prepended to get one or two bonus dice.

!cthARoll and !cthadv are for skill advancement.


!cthRoll 50     //roll against a target of 50
!cthRoll bb:60  //roll against a target of 60 with 2 bonus dice
!cthARoll 30    //advancement roll against a target of 30

User Variables

Users can store variables for use with the Storytelling dice pool system. Variables are stored on a per-room, per-user basis in the database (currently located in the cache directory if using the Docker image).


!set myvar 5 //stores 5 for this room under the name "myvar"
!get myvar //will print 5

Variables can be referenced in dice pool and Call of Cthulhu rolling expressions, for example !pool myvar or !pool myvar+3 or !cthroll myvar. The Call of Cthulhu advancement roll also accepts variables, and if a variable is used, and the roll is successful, it will update the variable with the new skill.

Running the Bot

The easiest way to run the bot is to use the official Docker image, although you can also run the binary directly.

A typical docker run command using the official Docker image should look something like this:

# Run unstable version of the bot
docker run --rm -d --name dicebot \
-v /path/to/dicebot-config.toml:/config/dicebot-config.toml:ro \
-v /path/to/cache/:/cache \$VERSION

The Docker image requires two volume mounts: the location of the config file, which should be mounted at /config/dicebot-config.toml, and a cache directory to store the database and client state after initial sync. That should be mounted at /cache/in the container.

Configuration File

The configuration file is a TOML file with three sections.

home_server = ''
username = 'thisismyusername'
password = 'thisismypassword'

path = '/path/to/database/directory/'

oldest_message_age = 300

The [matrix] section contains the information for logging in to the bot's matrix account.

  • home_server: The URL for the Matrix homeserver the bot should log in to. This should be the proper hostname of the homeserver that you would enter into the login box, which might be different than the server name that is displayed to other users.
  • username: Bot account username.
  • password: Bot account password.

The [database] section contains information for connecting to the embedded database. Note: you do not need this if you are using the Docker image.

  • path: Path on the filesystem to use as the database storage directory.

The [bot] section has settings for controlling how the bot operates. This section is optional and the settings will fall back to their default values if the section or setting is not present.

  • oldest_message_age: the oldest time (in seconds) in the past that a message can be before being ignored. This prevents the bot from processing out-of-context old commands received while offline. The default value is 900 seconds (15 minutes).

Running Binary Directly

If you have built the application from source, you can invoke the dice bot directly instead of using Docker by running dicebot /path/to/config.toml. By default, the user account cache is stored in a platform-dependent location. If you want to change the cache location on Linux, for example, you can run export XDG_CACHE_HOME=/path/to/cache before invoking the bot.

Installing the application directly also installs dicebot-cmd, which allows you to run arbitrary bot commands on the command line. This does not connect to a running instance of the bot; it just processes commands locally.

Future plans

The most basic plans are:

  • Resource counting: creation of custom counters that can go up and down.
  • Perhaps some sort of character sheet integration. But for that, we would need a sheet service.
  • Use environment variables instead of config file in Docker image.


This was orignally a fork of the axfive-matrix-dicebot, with support added for Chronicles of Darkness and Call of Cthulhu.