Working on this just for personal use, because my group really dislikes BRP. Just sharing in case others want some Cthulhu Mythos without using BRP. Updated with Mythos Tomes, rules for Mythos study and spells. There is an example of the Grimoire, to allow players to put the a5 pages into a spell book. Not releasing it completely as it's mostly copy and paste from CoC. The character sheet is set up, so you can write and print directly from the pdf.

Cthulhu Mythos hack

Mythos Grimoire example

Investigator sheet

Ideas are welcome, but the intent is to change the engine of CoC while still staying true to the general feel of the game, so it's not just Cthulhu in the Genesys system.

Here's my conversion files for all Masks of Nyarlathotep NPCs and items in the Mitnal , New York , Mauretania , London (including Burning Within ) and Cairo chapters. The rest will be uploaded once I've finished the PDFs.

God of Mitnal

New York

Mauretania

London (and Burning)

Cairo

The layout of the cards look good but the background competes heavily with the text which makes it difficult to read. Consider lightening up the background by 40% or so.

6 hours ago, lyinggod said:

The layout of the cards look good but the background competes heavily with the text which makes it difficult to read. Consider lightening up the background by 40% or so.

Yeah I know, noticed it myself Yesterday after exporting the pdf. It will most likely be even worse, when it's printed. It will be better for the next update.

Updated with all the tomes from the core CoC book.

• Fixed a few errors and made some minor tweaks.
• Included a new Pain & Injury system.
• Updated character sheet, weapons and rules to reflect the new Pain & Injury system
• Included a Conflict Sheet to make tracking easier
• Working on: Chase rules and vehicle statistics.

Updated with chase mechanics, vehicle stats and a vehicle sheet.

Nice work, good read. Definitly going to use some of that for my campain.

On 6/11/2017 at 3:14 PM, player1303422 said:

Nice work, good read. Definitly going to use some of that for my campain.

If you're running the Masks campaign, let me know. I have a couple of houndred Pages of conversion stats to the NDS system, custom handouts etc.

32 minutes ago, Gallows said:

If you're running the Masks campaign, let me know. I have a couple of houndred Pages of conversion stats to the NDS system, custom handouts etc.

As soon as I have the book and the die, I'll dive into that. Let's hope I dont delve too deep!

1 hour ago, player1303422 said:

As soon as I have the book and the die, I'll dive into that. Let's hope I dont delve too deep!

It's a brilliant campaign, but quite long. Apart from the opening scene, it's very open, with some great mysteries.

A new MoN edition is comming next year, so look forward to seeing what they have changed.

If I were to pick one long campaign to play it would be this or Eternal Lies (Trail of Cthulhu).

Once I'm done with everything for MoN, I'll add some rules option, so it can be used with Nights Black Agents as well, because there are a few mechanics like Heat for instance, that are quite cool for that setting (or any Independent investigator game really). It will require a few custom Agent Talents though, because the agents of NBA are quite badass compared to CoC investigators.

Updated with some Agent Talents and a few minor tweaks.

Don't mind the empty pages and the empty "Other Vehicles" page

very nice

Thanks Zhentil. Working on the rest of the Agent Talents (Aiming for 100 talents). When the talents are done, I'll do the other vehicles and finally get around to balance the whole thing. As it is now, the balance is a rough estimate of how I want it, so it will be tweaked once it's all done. I'll most likely also reorganize the document to make it more reader friendly instead of this "personal notes" style.

This is really good stuff! I'm not quite sure I follow the advancement rule though. It says

Quote

To increase a skill marked for advancement you roll a number of (green) equal to your skill and if you fail, you may advance the skill by one point (up to 5).

So you actually want to fail the check? I think I get the idea: it makes the check progressively more difficult. But it's an atypical check in that it doesn't use purple dice in opposition and you actually want to fail. Perhaps you could roll the check pitting your number of green dice (G) against (G+1) purple? At least then you'd actually be trying to succeed.

Do you use your advancement mark even if you cannot progress the skill?

20 minutes ago, Dragonshadow said:

This is really good stuff! I'm not quite sure I follow the advancement rule though. It says

So you actually want to fail the check? I think I get the idea: it makes the check progressively more difficult. But it's an atypical check in that it doesn't use purple dice in opposition and you actually want to fail. Perhaps you could roll the check pitting your number of green dice (G) against (G+1) purple? At least then you'd actually be trying to succeed.

Do you use your advancement mark even if you cannot progress the skill?

That's right from CoC (BRP really). You check skills you use successfully and meaningfully, at the adventure's end you roll against the checked ones, any you "fail" at means you learned something - add +1d10 points. If feels a bit less awkward in CoC only because the dice are a simple d100... not meant to generate an opportunity for narrative.

Personally, I'd drop it in the hack. Just advance normally.

44 minutes ago, dlw32 said:

That's right from CoC (BRP really). You check skills you use successfully and meaningfully, at the adventure's end you roll against the checked ones, any you "fail" at means you learned something - add +1d10 points. If feels a bit less awkward in CoC only because the dice are a simple d100... not meant to generate an opportunity for narrative.

Personally, I'd drop it in the hack. Just advance normally.

But normal advancement means you can advance any skill anytime you have XP, not just ones you actually used. I actually kinda like the "use it to improve it" vibe, but not the "roll a check and fail for the win!" implementation here. Make it success-based.

I’d base it on advantage/triumph somehow. When you use a skill during play, you can spend an advantage to say you learned something, pass or fail, and get a tick next to the skill. At the end of the adventure, or whenever, if you have accumulated enough of those ticks, you (may?) raise the skill. Creates a decision during play, spend advantage for immediate benefit, or to to improve long term. Only downside would be players concocting silly reasons to use skills when it doesn’t matter, just to get the advantage in a non critical roll.

As a GM you can award a player with black, purple or red dice for advancement checks as a reward for doing something clever with the skill.

I like this advancement system for CoC, since it means getting to 5 in a skill is really quite elite. Making it success based would not really work. With a low skill your chances of getting an advancement is lower, but as your skill increases the chance of learning from that advancement becomes more difficult. It's not really pretty with the NDS, but from a mathematical point of view it works The reasoning behind it is that as you begin mastering something, progress becomes slower and some people may never reach an elite skill level. Instead if thinking of it as a failure, consider it a test to see if whatever bright idea you had during the session was actually something new or ground breaking for your character. If you succeed the advancement test you already knew the clever idea you had, but just used it in a different way perhaps.

I would have used purple dice on the advancement test and then award positive dice as a bonus, so it isn't so wonky ? Unfortunately the probability on the purple die is 3/8 whereas it's 4/8 on the green. I'll see if I can work it out, because the current curve is fine, but failing seems odd in this system I agree ?

there will be more explanation and advice once the core stuff is done. Still have a lot of stuff in one-note, but since we're already playing with the system I just put stuff in there so my players have access to the rules.

I have Pages of feedback from our sessions and what people have written here and elsewhere. Once the base is done, I'll go through everything and try to tweak it before reorganizing and making the document more readable.

EDIT: Great idea Forgottenlore, cheers

Advancement math:

1 green = 50%

2 green = 25%

3 green = 12.5%

4 green = 6.2%

A different system could either use intellect for all or an appropriate characteristic against the skill level. That would take into account natural ability to learn, so perhaps the characteristic against the skill level in red dice. Perhaps testing against the skill rank you're trying to get to.

Lets try with an average characteristic of three.

1 red = 66%

2 red = 46%

3 red = 30%

4 red = 19%

5 red = 12%

A characteristic of five

1 red = 86%

2 red = 72%

3 red = 56%

4 red = 42%

5 red = 30.6%

Not quite what I like for long term play, but perhaps something along those Lines where success grants an advance.

maybe just Rolling three green against the new skill score of red dice would be fine. Blue dice for advancement rewards.

Added an additional 30 Agent Talents for a total of 79. More may be added later. I'll add trucks and other vehicles on the empty Other Vehicles page.

Next I'll go through the document, fix errors and reorganize the document with more explanation to make it more reader friendly.

Once I have the Genesys book, I'll go through the rules again and tweak, change and add based on those rules.

Added some trucks, horse and carriages, motorbikes and a bicycle. Updated the vehicle sheet to include pdf text fields to input stats. Exported the character sheet as a separate pdf. A few minor tweaks.

Updated the original post with conversion files for all NPCs and items in the God of Mitnal, New York, Mauretania, London and Cairo chapters of Masks of Nyarlathotep. Rest will be uploaded when the PDFs are done

Hey I just wanted to say that even though no one else have replied in a while there are those of us who really appreciate people doing these conversions, and Call of Cthulu is definitely something I'll want to keep an eye on. Have you made any progress since November 25th?

Id like to know as well, thanks for all this work!

Still working on it, but work has been insane, so had to put it on hold for a few weeks.