I had some thoughts about Mythos skill while listening to some podcast or other - I can't remember which one now. Possibly RPPR. You can read a tome about Hastur and suddenly know about Ithaqqua. Or you can sometimes know about byakhees, and sometimes not. It's weird.
An idea came to me that you could introduce a fractal approach to Mythos skills (and indeed others, but let's stick with Mythos for now). This would be a tweak specifically for games where there's quite a lot of Mythos going on, and particularly suitable for long-term campaigns focused on a subset of the Mythos but including elements from other factions.
Basically, there would be a core Mythos skill, called simply Mythos. This is a generic skill that you can always use which works exactly like Cthulhu Mythos does now.
There would also be branching sub-skills which sit on top of that when they are relevant to the roll. Examples would be:
- Azathoth Mythos
- Cthulhu Mythos
- Gla'aki Mythos
- Hastur Mythos
- Ithaqqua Mythos
- Nyarlathotep Mythos
- Y'golonac Mythos
- Yog-Sothoth Mythos
You would gain points in the sub-Mythos skills when you have experiences (including reading tomes) that relate primarily to that faction. So if you read The King in Yellow, you would gain Hastur Mythos rather than Mythos, and those points would help you only on Hastur-related rolls. The Necronomicon on the other hand would continue to grant Mythos skill.
So for example, popular weird fiction author Mick Narsh has read The King in Yellow and also had hair-raising encounters with ghouls. He has 6% in Mythos, and 5% in Hastur Mythos. When confronted with a strange pale woman wearing a peculiar badge, he adds them together and rolls on 11% to identify her as a Hastur cultist.
We could even take things further - once you go fractal, why go back...tal? Certain entities or species are specifically associated with a particular deity. If Deep Ones are heavily tied to Cthulhu, they might form a sub-branch of Cthulhu Mythos. R'lyeh might form another. In a campaign focused heavily on the Cthulhu side of the Mythos, and particularly one where Investigators can learn a great deal, this might provide an interesting way for them to build up considerable knowledge of their antagonists. At the same time, it avoids the head-scratcher where all that Deep One exposure somehow teaches them about the Servants of Gla'aki.
(I can't get nested bullets to work correctly, boo, apologies for formatting)
** Azathoth Mythos
** Hastur Mythos
*** King in Yellow
** Ithaqqua Mythos
** Nyarlathotep Mythos
*** The Bloody Tongue
** Y'golonac Mythos
** Yog-Sothoth Mythos
If you did go to that third tier, I'd probably want to adjust the way X Mythos is obtained. I'd tend to suggest that exposure to Deep Ones grants, say, 5% right off the bat. Listening to old Zadok ranting about them gives you a hefty whack of 15% or so. Listening to the cousin locked away in the asylum tell you about his dreams gives you another 10%. Most conversations would be less infodumpy so you'd pick up substantially less, maybe 1d3%.
Basically, I'd make it relatively easy to learn about the "common", relatively-human races. What those skills are going to let you do is primarily recognise their artefacts, the signs left by their plots, a little bit about their cultures and activities, and the creatures themselves. Useful, but not overwhelmingly so, as it doesn't particularly grant an advantage to dealing with the problem. It makes sense to me that having encountered Deep Ones in one scenario, you'd find it relatively easy to recognise another Deep One colony three scenarios down the line.
Another potentially-interesting application here would be if you wanted to run a slightly broader weird campaign that wasn't focused only on the Lovecraft Mythos, and that didn't take the common tack of folding everything into the Mythos somehow. In this situation, you could actually establish other primary branches to sit alongside Mythos. For example, in a game featuring both the Lovecraft Mythos and a fairly traditional sci-fi element, you might have an Aliens branch, whilst in one with a strong fantasy element you might have a Faerie branch.
What about Sanity?
I suppose I envision this kind of mechanic as one where people would end up with relatively large amounts of skill points in the sub-Mythos skills. As such, we need to think how Sanity is going to work.
I'd honestly rather not have the sub-skills demolish maximum SAN to quite the same extent, because that would make it difficult to build up significant amounts of points in more than one faction without going insane. Since this is supposed to be a more nuanced version of the existing Mythos skill, and those X points in 3 factions correspond closely to X points in the existing Mythos skill, they should probably be weighted.
My inclination is probably to say that maximum Sanity would be affected as normal by Mythos points, but that sub-Mythos only caps Sanity for every five points. So gaining 10% in Hastur Mythos would reduce your maximum sanity by 2. Depending how many branches and sub-branches you want to use, this could be less (if only two factions will feature in the campaign, try half) or much more (if you're using a dozen Great Old Ones, use one-tenth). If you want to use sub-sub-skills like Deep One Mythos, I'd reduce those even further.
Is it worth it?
I'm not sure whether this is something I'd actually use - but then I haven't yet managed to run a single campaign, so it's hard to know whether it would be useful. I feel like for a campaign that's very heavy on Mythos content it might add some flavour and granularity; on the other hand, Call of Cthulhu is all about non-granularity with a simple, if swingy, ruleset.
Tracking skills that might hit three-deep levels of nesting is not simple. For people who enjoy that granularity, great. For other people, less great.
In theory you could use a similar system for other skills. It struck me that it might be nice for those who favour a more detailed approach to firearms, and of course you could apply it to scientific or historical skills in a campaign leaning heavily on those. Perhaps that new Time to Harvest thing I'm hearing about, centred on in Miskatonic University?
The difficulty of using it with other skills would be deciding how points would work. It's simple with Mythos, which you simply get. On the one hand, a more specific skill should be cheaper because it's less useful; on the other, that's easily gamed with some skill types, particularly combat skills. For example, someone who plans to use a specific weapon could put all their points into that rather than generic Rifle, because they will only use the XYZ Rifle anyway. That doesn't really work for most other skill types, which aren't as fungible - you can't really use Modern Persian History to roll Ancient Colombian History, for example.
Does this seem like an interesting idea? Would anyone use something like this?