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Conversion Guidelines for BRP/CoC to Mythras?


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I have a boatload of assorted BRP/RQ/CoC supplements, and I was wondering if there was a handy guide to doing conversions?
For magic I would simply use the sytems from Mythras without trying to do too much direct conversion, so I am mainly thinking of characteristics and skills.

It looks like Characteristics are almost identical, at least for human-level characters, so that's not too big of an issue. Just copy/paste the values and calculate the attributes from them.

Are skill levels roughly equivalent? I.E. should I just average a character's martial skills and give him a combat style, or are the assumptions of skill levels lower/higher for Mythras?

I think converting is pretty straightforward, maybe fiddling around with traits and special creature mechanics to fit better into Mythras for CoC monsters. But right now I'm only looking to convert over largely non-supernatural human beings.

Edited by VonKatzen
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well, I would say a 50% in any skill is going to map to a 50% in the other system. it's a chance for success - so, yes, equivalent. For combat skills, I would do as you suggest. i might just kind of eyeball it even.

the base in Mythras skills might be a bit higher - it's derived from stats and not as a flat percent to start with. Most of the skills that start at 05% in BRP are professional skills in Mythras, and you don't get a chance at all. as an example, Stealth in BRP starts at 10% - in mythras it's DEX+INT, which for humans is a minimum of 11 with the lowest INT and DEX possible, and human average would be more like a 24. 

iirc, one time I mapped out the character creation process, and Mythras got more points than CoC characters. Closer to Pulp Cthulhu, but without the powers.

EDU doesn't exist in Mythras. I'm not sure how I would map that, or even if I would. Luck exists, but is different entirely. Magic points are the same I think. Hit points are going to change, so I would just use the mythras ones. it should be easy to calculate.

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EDU would map to some Education skill, which for many countries would be a Standard skill.  I think we discussed a related topic a bit on the TDM forum.

Yes, my general impression is that in most cases a *starting* Mythras character is going to have mostly higher tallies in most skills than a *starting* BRP character.  However, I have often thought that our old RQ3 (~ BRP) characters *advanced* much faster in their most-used skills, because of the "checked boxes" versus "Improvement Points" philosophies of the two systems.

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Converting skill stats is not that complicated. 

The main problem i have is the suggested rolls in adventures: 

If a BRP-Adventure for instance states that this situation required a DEX x 2 roll to jump out of danger, i assume that this will be a roll on Evade. But is DEX x 2 converted into a Hard, Formidable, something else?

A simple DEX roll (DEX x 5) is for the average Person against 55% (DEX 11 x 5), but can be in between 15 and 90, but that are extremes. Lets assume that DEX is somewhere in between 6 to 15 --> 30 to 75%. 

Since the average DEX in MYTHRAS is the same (11) and 6 to 15 is likely, the base chance can be everything in between 12 to 30%, on average 22%. 
An Easy Evade roll would become a 42%, and a Very Easy a 62% for ther average DEX 11 guy. 

So MY conversion would be: 

DEX x 5 = Very Easy
DEX x 4 = Easy
DEX x 3 = Standart
DEX x 2 = Standart
DEX x 1 = Hard or Formidable

But this is only for DEX converted to Evade. 

The outcome may differ for other skills. 

If the skill of the average adventurer is likely to be higher than the base chance due to his culture, and/or occupation it will be different from skills that are likely NOT to be raised during character creation. 

It´s more complcated than it seems at first glance. 


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I use the Luther Arkwright rules for all my CoC adventures as the Tenacity Rules map vary well to the CoC sanity. I use EDU as advanced skill that helps augment any skill that Lerned in a library, if they have Access to the library or books. Luck I use as stated in the Mythras rules.

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