D20 Modern + Cthulhu D20: What would you do?

[Chainsaw Mage]

In a few weeks I'll be running a Call of Cthulhu one-shot adventure (d20) and I'm debating whether or not to use D20 Modern (and just take the Sanity rules and, obviously, the Mythos from CoC). CoC d20 has its own character creation rules (and even a unique skill list, which includes "Operate Heavy Machinery" as its own skill :\ ) and I'm pretty stuck in D20 Modern. However, does anyone foresee a problem using the D20 Modern classes for Call of Cthulhu d20? The combat systems are more or less identical (and I use D&D 3.0 subdual damage in Modern anyway, so that's no problem).

One thing's for sure...no D&D style magic in my CoC d20 game!

 

[takyris]

Only issues I can think of:

1) People are a bit more durable in d20 Modern. Their defenses will be higher, so if you fling monsters at them, don't hold back. On the other hand, d20M saves are generally a bit lower, so Will saves and Fort saves are pretty nasty. Expect people to blow them a fair amount of the time. If you're going for scariness, lots of monsters that do a little damage (2 claws for d4+1 apiece, for example) are better than a monster that can do a lot (1 slam for 2d6+5 or something), because that big guy can take somebody out in one hit. A mixture is always appropriate, but the one hit guy shouldn't be the regular normal baddie.

2) I believe that CoC character creation is a bit easier, so if you're gonna have people make up characters on the spot, it's easier to use CoC stuff -- unless, of course, they all know d20M already.

3) Decide right away whether you want to use 10 or Con as your MDT, and whether you want a failed save to kill you or take you to -1. I personally tink that Con and -1 are fine, even for CoC, but mileage may vary.

4) Unless you're making PCs yourself, stress to folks how important skills are. CoC isn't as much fun when the PCs are all Strong/Fast martial artists. It's best when you've got Smart/Dedicated or Charismatic/Fast people running around trying not to die. This is why I tend to make characters for my players in one-shot adventures like this. And, to be fair, you should legitimately make skills important and helpful, so that the Smart/Charismatic guy doesn't feel like a loser when he can't hit the zombies with his revolver.

5) Stat up good improvised weapons for d20 Modern -- stuff that is better than normal improvised weapons but not as good as a Simple weapon. People are gonna want to grab stuff. For example, I statted a sledgehammer as an Archaic weapon equivalent to a normal warhammer but requiring two hands to use (since, well, it's not built for combat). This means that a "no combat training" PC who grabs it is swinging at -4 for 1d8, but somebody with archaic weapons proficiency might find it an actual useful tool.

Hope this helps!

 

[Chainsaw Mage]

Only issues I can think of:

[tons of excellent advice snipped]

Hope this helps!

Takyris, that was *exactly* what I was hoping for. Thanks a ton! Since you seem to have a very good grasp of both games, tell me this: are the firearms rules in Cthulhu d20 (which seem VEEEERY detailed) the same in D20 Modern, or did Modern come up with different firearms rules?

 

[takyris]

Well, this is the part where I get out of my depth, but my understanding was that there were some pretty big differences.

In d20 Modern, guns are pretty vanilla -- almost all handguns do 2d6, while longarms do 2d8 or, for the big stuff, 2d10. The differences are pretty minor -- one gun is mastercraft (+1 to hit), while another has a slightly longer range (40 feet instead of 30), and still another has a larger clip. There's really no "best gun", and people getting shot with guns isn't a death sentence (2d6 damage is only likely to threaten a massive damage check if you roll a critical). In CoC, I believe that guns are a fair amount more lethal, and since you're only trying to crack 10 on the massive damage check, that's even more deadly.

It's... well, I guess the right way to say it is "In d20 Modern, if you don't have several feats invested in something, it's assumed that you're not very good at it." So in theory, a goon with personal firearm proficiency can have a gun trained on a heroic PC, and the heroic PC isn't in that much danger -- the goon still has to hit him with the attack, and it'll only do 2d6 damage, which probably won't threaten an MDT on an athletic hero.

On the other hand, a major villain with some levels will be holding that gun on the PCs, and he'll have Point Blank Shot and Double Tap, and maybe Mastercraft +1 damaging bullets, so he'll be doing 3d6+2 (Double Tap adds 1 die of damage, PBS adds 1, Mastercraft adds 1), which is far more likely to kill a hero with a single shot.

Personally, I like this. I like my heroes to be able to take out a single lackey with a gun, while still comfortably nervous when confronted by ten lackeys with shotguns (2d8, and you know that one of them will hit). For d20 Modern, this is about the level of Heroic vs. Realistic that I want.

For CoC, though, you might want to have even high-level people be terrified of a single cultist with a gatling gun -- which, if I recall correctly, is one step from "okay, forget the damage, just save or die", for all intents and purposes. It's easier to threaten people that way.

CoC also uses different Autofire rules. I don't remember them offhand, but they are, well, different. I personally am fine with d20 Modern's autofire rules, but you might wanna see which one gives the right "feel" for your game.

EDIT: PS: Glad I could help. Sorry I don't know more about the details of the CoC stuff offhand. My players and I looked at it, played around with it a bit, and then opted to just go with d20 Modern plus Sanity, like you were suggesting. But that's because my players already know d20M really well. The situation could be hugely different for people new to either system.

 

[Achan hiArusa]

Firearm rule differences

In CoC burst fire is +1 attack action with the gun with a -4 to hit (if you have the multifire feat its -2 to hit). Automatic fire is +2 attack actions with a -6 to hit (if you have multifire again then its -4 to hit).

In Modern d20 to get any effect out of burst fire or automatic fire you must have the feats (Double Tap and Burst Fire). Double Tap does +1 die of damage with a -2 to hit, Burst fire does +2 die of damage with a -4 to hit, and you have to have advanced firearms proficiency in order to use either of those feats.

Also, Modern d20 guns usually do more damage, they have lower critical multipliers (all are flat x2 in Modern, whereas it depends on the gun in Cocd20).

Personally I throw them all together into one mismash in my games. I use the Coc rules and character's with the feats above also gain those bonuses. I also use the critical ranges from Pulp Heroes and the Shadowchaser's Polyhedron along with the critical multipliers from CoCd20 for any modern game I run.

However, for my CoCd20 games, I just keep to the rules, except that I use the BRP hit point rules (hp=Con, heal 1d3 damage per week) and I ignore challenge ratings instead giving out story awards like in White Wolf. I have been tempted to create a combat option for those who are more willing to die...er...fight.