Working on a Call of Cthulhu/D20 Modern/E6 Mashup

[Dusk Raven]

So, as sometimes happens, I've been inspired to run a particular d20 variant – in this case, the somewhat obscure Call of Cthulhu d20 book released back when 3.0 was a thing. However, since it has its flaws, and I enjoy tweaks and homebrews anyway, I've decided to mix it with other d20 versions.

To start with, I think E6 works really well for this. Whether you're using the base CoCd20 system or just porting eldritch horrors into D&D proper, I think giving characters a low level cap really fits with the theme of any horror game. The player characters may become more skilled through feats, but they'll never go above a certain level of durability or raw power.

The second thing I wanted to add to this mix combine was d20 Modern. It has its flaws, but I've always sort of liked it and wished it had more support, and I certainly think it's more interesting than, say, the way classes are handled in CoCd20. To some extent, though, I think I'll probably mix and match rules from each. I'll largely go with d20 Modern, but I think the firearms rules from CoC are better, for instance. Or at least, they made more sense to me. I will also note that I may be willing to go with any good d20 Modern fixes that are out there.

...There is one modification I want to make that deviates from both systems, and it's to the Sanity rules. Honestly, the system of Sanity in Call of Cthulhu doesn't really appeal to me. It just looks to me like a constant cloud of Save-or-Die hanging over the party that will inevitably result in players having to make new characters, and while that does produce an atmosphere of “contact with the Mythos should be avoided” as well as the feeling that any encounter could prove fatal, but I'm not really sure what a given party is supposed to do about that. It also provides an incentive not to overuse spells, and that I get, but... I feel like it should be something less imminent, that players should only go insane if they've really pushed the envelope. But then again, I disagree with several basic tenets of Lovecraft's work, among them the idea that the eldritch beings beyond our knowledge will inevitably drive humans insane. I also don't know what system I would replace it with. I may go with something more mild, having it so that Sanity losses are less dire... but at the same time, I keep a player's Sanity score hidden from them, to keep them on their toes – and the lower their Sanity goes, the more I start passing them special notes...

Anyway, those are my thoughts so far on trying to breathe life into a largely ignored d20 variant. Thoughts? Suggestions? Condemnations?

[ColorBlindNinja]

I will say that I've been pleasantly surprised by d20 Call of Cthulhu. The system more or less does what it's designed to do.

It's actually very difficult to kill Mythos monsters at all, save for the really low CR ones.

Some of the weapons in d20 Future might allow the PCs to punch above their weight class, so to speak, but I'm guessing you're running this campaign in modern day, so that shouldn't be an issue.

One potential issue: Cthulhu and Modern have very different rules for automatic gunfire.

d20 Modern has you take feats to actually get a benefit from automatic gunfire. One feat adds an extra damage die to semi auto guns and the other gives you 2 extra damage dice for automatic ones.

Meanwhile, d20 Call of Cthulhu merely gives you extra attacks with semi and automatic firearms.

EDIT: But you take a penalty to hit with those extra attacks.

[Dusk Raven]

I will say that I've been pleasantly surprised by d20 Call of Cthulhu. The system more or less does what it's designed to do.

I think it might actually be most interesting in the context of a D&D setting with Mythos entities as the primary source of monster, and the book provides some interesting information about that very premise. I would absolutely love to play in a D&D campaign of that nature. I will, of course, settle for a d20 Modern game too.


Some of the weapons in d20 Future might allow the PCs to punch above their weight class, so to speak, but I'm guessing you're running this campaign in modern day, so that shouldn't be an issue.

Modern day at the latest. Really, a lot of time periods work well for this, but I'd favor either the beginning of the "War on Terror," the height of the Cold War, or good ol' late 20s/early 30s.


One potential issue: Cthulhu and Modern have very different rules for automatic gunfire.

d20 Modern has you take feats to actually get a benefit from automatic gunfire. One feat adds an extra damage die to semi auto guns and the other gives you 2 extra damage dice for automatic ones.

Meanwhile, d20 Call of Cthulhu merely gives you extra attacks with semi and automatic firearms.

EDIT: But you take a penalty to hit with those extra attacks.

As stated, I somewhat prefer d20 Call of Cthulhu's rules. d20 Modern does allow characters to make small AoE attacks with automatic weapons, but so far as I know they don't really scale and I've heard they're underpowered at higher levels.

[ColorBlindNinja]

I think it might actually be most interesting in the context of a D&D setting with Mythos entities as the primary source of monster, and the book provides some interesting information about that very premise. I would absolutely love to play in a D&D campaign of that nature. I will, of course, settle for a d20 Modern game too.

How funny that you mention that, since I'm trying to do something similar but with Mass Effect and Star Wars thrown in. (http://www.giantitp.com/forums/showthread.php?577033-Massive-d20-Crossover-Advice-amp-House-Rules)




Modern day at the latest. Really, a lot of time periods work well for this, but I'd favor either the beginning of the "War on Terror," the height of the Cold War, or good ol' late 20s/early 30s.

Right, then d20 Future shouldn't be an issue.


As stated, I somewhat prefer d20 Call of Cthulhu's rules. d20 Modern does allow characters to make small AoE attacks with automatic weapons, but so far as I know they don't really scale and I've heard they're underpowered at higher levels.

The to hit penalties can be a problem, especially at low levels. But I suspect that all firearms will be underpowered at higher levels.

[Dusk Raven]

How funny that you mention that, since I'm trying to do something similar but with Mass Effect and Star Wars thrown in. (http://www.giantitp.com/forums/showthread.php?577033-Massive-d20-Crossover-Advice-amp-House-Rules)

...Huh. I should look into that. Also, you just reminded me - one thing I'd seen recommended for d20 Modern is to use the Wound and Vitality rules from the Star Wars d20 game. I may incorporate that too...


The to hit penalties can be a problem, especially at low levels. But I suspect that all firearms will be underpowered at higher levels.

Well, not if you don't have any other options. Then again, this is Call of Cthulhu E6, everything the players have is underpowered at higher levels!

[ColorBlindNinja]

...Huh. I should look into that. Also, you just reminded me - one thing I'd seen recommended for d20 Modern is to use the Wound and Vitality rules from the Star Wars d20 game. I may incorporate that too...

A word of caution, under vitality and wounds, critical hits become very deadly.


Well, not if you don't have any other options.

Speaking of, are you allowing content from Urban Arcana?


Then again, this is Call of Cthulhu E6, everything the players have is underpowered at higher levels!

True enough. :smallbiggrin:

[Dusk Raven]

A word of caution, under vitality and wounds, critical hits become very deadly.

Which is, I think, fine for the mood of Call of Cthulhu.


Speaking of, are you allowing content from Urban Arcana?

My gut says no, mostly because, so far as I know, it mostly adds "classic" fantasy stuff that wouldn't really fit for a standard Call of Cthulhu setting. Its magic also tends to be more powerful than the spells in CoCd20 (which is admittedly a complaint I have with the spells in CoC - they're situational/weak AND they cost sanity and/or ability points?). It would, however, work very well for a "Lovecraft Lite" (https://tvtropes.org/pmwiki/pmwiki.php/Main/LovecraftLite) setting where humans could, for instance, use magic without harm and make alliances with nonhuman beings, and thus can stand against cosmic horrors.

...That's actually starting to appeal to me now. Though, I have a different setting that would also fit Urban Arcana...

[ColorBlindNinja]

Which is, I think, fine for the mood of Call of Cthulhu.

Fair enough.


My gut says no, mostly because, so far as I know, it mostly adds "classic" fantasy stuff that wouldn't really fit for a standard Call of Cthulhu setting. Its magic also tends to be more powerful than the spells in CoCd20

I heard the magic in Urban Arcana isn't that great.


(which is admittedly a complaint I have with the spells in CoC - they're situational/weak AND they cost sanity and/or ability points?).

Yeah, that is true. CoC does have a few good spells, but they're mostly intended for NPCs.


It would, however, work very well for a "Lovecraft Lite" (https://tvtropes.org/pmwiki/pmwiki.php/Main/LovecraftLite) setting where humans could, for instance, use magic without harm and make alliances with nonhuman beings, and thus can stand against cosmic horrors.

...That's actually starting to appeal to me now.

I guess it really depends on the genre of game you want to run.

[Ruethgar]

For some reason I'm just thinking of a youtuber that read Shadowrun stories and thinking how fitting the insane "spellcasters" would be for this. Staying a bit closer to home, if you wanted magic, I would suggest gaining it only through unavoidable Taint(i.e. no undead or ritually ascociate with Evil to avoid the effects).

Spheres of Power also offers options for customizing magic to make it more punishing to use such as addictive casting or just more difficult such as strenuous and mental focus. Custom wild magic effects might server a similar purpose, I made a vampire that has a significant chance to go into a frenzy when he uses magic and slaughter everything that moves, but the magic is also addictive so he needs to cast or suffer. Have another character for a lower magic world that took all of the time increasers to be more like a ritual caster than a magic gatling gun.

I also had a world where all spellcasters had the effects of Methodical Magic Methods, and Arcane Fatigue added to their magic. Another still that made most spells Whispering Way spells(negative level on cast), forcing them to take Enduring Life asap or become a Wight. For that reason, magic was viewed with great suspicion and people assumed you would bring about a plague of undeath by spellcasting. That world was rather deadly, so many undead.

[Dusk Raven]

I heard the magic in Urban Arcana isn't that great.

Oh. Well, it's not like I'd know from a quick skim.


Yeah, that is true. CoC does have a few good spells, but they're mostly intended for NPCs.

That makes sense - hostile NPCs (and especially cultists) don't need to worry about Sanity.


I guess it really depends on the genre of game you want to run.

I think the best way to describe what I want to run is, "A Call of Cthulhu game where taking the side of the Outer Gods, or giving up one's own humanity to become a mythos creature oneself, is a viable (if risky) option." Everything else - the time period, how horrible the eldritch horrors really are, or even whether or not it takes place in the Cthulhu Mythos itself - can be decided later.

...It is kind of fun to toy around with possibilities until the final decision, though. The very game that inspired me to go on this train of thought has also inspired me to try and mix Lovecraftian Horror with a post-apocalyptic world (adding d20 Apocalypse to this mix). Haven't seen that a whole lot before, other than maybe Metro 2033... anyway, the Earth being at risk of destruction by powerful alien entities doesn't seem as bad when the Earth is in pretty bad shape to begin with.

[Bohandas]

...There is one modification I want to make that deviates from both systems, and it's to the Sanity rules. Honestly, the system of Sanity in Call of Cthulhu doesn't really appeal to me.

Agreed. Plus it doesn't actually fit with the literature; it makes things a lot closer to Birdbox than to anything written by Lovecraft and his circle of friends. The majority of characters who wind up in mad houses in the original Cthulhu Mythos stories are there because they were incorrectly assumed insane after accurately recounting somethig strange that happened to them. There were also several who were possessed (Wall of Sleep, Thing on the Doorstep, Shadow Out of Time, etc). And many of the ones who did go insane implicitly either had some kind of PTSD (or shellshock as it would have been called on those days) or else some kind of physical brain damage (for example the guy from The Repairer of Reputations fell off of a horse and hit his head. Although that particular story was by Chambers rather than Lovecraft)