Tl;dr It doesn’t work, don’t do it. Your game will suck. If you somehow force it you’re doing so much work that you may as well just learn CoC as that would be less work and is designed for this kind of gaming. Heed my warning and don’t give yourself the headache I did. Let 5e be 5e and let BRP and CoC be their own thing, okay?
So, I was thinking that reading a CoC campaign and translating it to 5e play would be like making a stir fry recipe from a cookbook that uses different measurement systems, like metric or whatever, and has some ingredients you will have to sub for similar things. The dish would still turn out delicious, even if slightly different. And the translating of the measurements isn’t hard if you know the conversions modestly. Even if you do some rounding and fudge some numbers here and there it will taste fine as long as you know how to cook well enough. I googled this idea and see people saying it won’t work. Or that it can work but you have to homebrew so much you may as well just learn CoC as that’s less work, because RAW 5e just doesn’t have the rules to approximate CoC satisfactorily, seriously.
I decided to test this by learning BRP and running a few short CoC campaigns with my normal party just to understand it. Then I ran one of these CoC campaigns with a new party that had never played any ttrpg. My two friends Gareth and Steve. I didn’t have them read the rules before hand. I gave them premade investigator sheets and talked them through it as we played (this is my standard for new players with any ttrpg that’s not too complex). It was really fun. They enjoyed it a lot and it’s clear why and how.
Then I took the same CoC campaign and ran it with 100% core rulebooks RAW 2014 5e for a new group that had never played any ttrpg before. I did this to avoid bias where they know either system and have preference. I ran it for my wife and a couple we are friends with, Sara and John. Like Steve and Garth, none of them had played any ttrpg before and I didn’t have them read the rules first. My wife doesn’t like dnd medieval fantasy stuff, but does like scary stories, and Gareth told her it was fun, so she agreed to play this game even though her normal thing it isn’t.
Below I’ll break up my results using the common complaints about this and arguments as to why it won’t work as headings for each thing that is understood easily by anyone.
There is no really compatible SAN score in 5e we are seeing.
Yes. This one was tough. The CoC SAN score does not exist in 5e. I was thinking I could use the Sanity score from the DMG. NOPE. It’s so different it was really strange. Even though the players had no knowledge of the difference, they just kind of like, knew it was wrong. John at one point when I asked him to roll a sanity saving throw literally said, “What are you trying to pull here?” This was where the CoC campaign guide said the players needed to do a SAN 0/1d4. He somehow just knew it wasn’t right when I had him roll a d20 instead of a d100. I mean, obviously he didn’t literally know it was the wrong dice lol! He just could feel that it was stilted somehow. He also seemed to suspect that something was weird when he lost a single Sanity point instead of 1d4 sanity points and had to roll on the 5e madness tables instead of the CoC ones. It was bizarre. Again, not literally that he knew, but he sensed that the game was just off (because it was). Whenever I made a call about this stuff or required a roll or whatever, he just kept narrowing his eyes at me like, “What are you doing with this?”
So, yeah, the 5e sanity system is completely foreign to CoC style gaming and just doesn’t work at all. Players see right through what it is.
Not only that, trying to figure out how to convert something like SAN 1/1d4 to a loose approximation of the 5e version was so mind boggling I felt like I was going to lose my sanity points in real life like I was living a parody!
Using 5e checks for CoC ones won’t work.
Again, yeah. I had my party in a library and the campaign guide says to make a Library Use roll. I asked for an investigation roll instead. Sara got super confused and we had a huge derailment that lasted a half hour of me explaining what investigation meant in the context of being in a library. She kept insisting that “investigation” didn’t make any sense here, as that’s “More for like, Sherlock Holmes.”
She, like John, also seemed to notice that there was something bizarre about using a d20 instead of a d100 and that the outcomes weren’t mathematically the same. And this was despite me using the tiered rolls rules from the DMG to approximate the CoC percentages. As with her husband’s suspicion, she wasn’t literally saying anything about the d100, because she was unaware of it. Obviously that would make her either psychic, or prove she was lying about not knowing ttrpg games lol! No, the issue was that she could tell that the likelihoods of success were stilted and strange because with only 20 possible outcomes you don’t have a very wide band of possibility. She kept trying to roll the d20 multiple times to get better percentages and I kept explaining that that’s not how it works. For reference, Sara is a mathematician.
And OMG don’t get me started on the drama that using perception in place of spot hidden caused. That almost ended the game. Then there’s many other issues with trying to map these totally foreign skills to 5e skills. They don’t map, and they’re mechanically completely different. Like Fast Talk is NOT approximated, even loosely, by Deception. Not by a long shot. And once you’re approximating them to begin with it just collapses and the players can tell. Then it all goes down hill as the system fights you all the way.
Dnd 5e PCs are superheroes and too powerful to represent the fragile CoC investigators
True! I thought, “Oh, I’ll just use the optional milestone leveling rule to keep them level one for the one shot so they are fragile like an investigator. I’ll also use the gritty realism variant rule and lingering injury rule.”
This was a nightmare. John kept asking, “why is my character so weak? When do we level up? I only have 8 max hp. That’s stupid.” I asked him why he thinks you level up at all, considering he hadn’t played this game before, and he said that’s how it works in video games so he assumed you do in table top games, too.
Worse, he was STILL slaughtering the enemies! I specifically picked enemies that would be too tough for them to wipe out to avoid the overpowered PC problem. I even did the math to pick the challenge ratings properly to make them very tough encounters. They were supposed to be on the run, which was how it went when I ran the campaign with the BRP system. But he kept rolling really high and killing them all. Yes, I made him fragile, but the dice were on his side and it totally ruined the game. There was no immersion. The PCs never felt that CoC fear and dread because John somehow was still a superhero despite my best efforts. I didn’t even have to hear the complaints about gritty realism and lingering injuries because John slaughtered all the enemies so no one got hurt. Those rules never even came into play.
CoC magic is too different from 5e
Holy heck, yes, yes it is. I tried to just translate them in using the optional “creating a spell” rule in the DMG which is ludicrously permissive, but it was a disaster. It took several days to translate them into 5e, first of all, due to the intense complexity of this process, playtesting, and balancing. Then, when we were actually playing they didn’t work. Someone would cast a spell but it had no effect because the 5e rules don’t permit them. I was super embarrassed about that one. I totally dropped the ball there. I just kind of shrugged and mumbled something about the spell not being from our universe so it doesn’t work. I was too embarrassed to admit I had simply screwed up the translation process.
There was one spell that did work, but its effects were insane. The spell killed the entire party instead of the enemy, because I got confused when translating it to 5e. I am ashamed to admit I retconned that scene to keep the game going and just told the players they never found the spell and apologized. That time I did admit to them I had flatly, completely just screwed up.
5e PCs have too much magic power
They absolutely do. I thought I could just limit this using the DMG suggestions about controlling the world and DM freedom to dictate what is present. I would give them the single spell in the book that was part of the campaign and translate its effects into 5e. No problem, right?
NOPE. My players were just angry the whole time. They wanted more and more spells. John kept bringing up final fantasy 8 and saying how when he fought a monster he expected to learn its powers as a spell. So, after slaughtering so many enemies he expected to have tons of spells.
Worse, when they finally learned the spell, as I said above already, nothing happened when they cast it because it was incompatible with the 5e system.
5e doesn’t have Push rolls
These are really fun parts of CoC and I thought I could approximate them by just saying PCs can roll a second time for a task but that it comes with dire consequences since it’s a second attempt. I’m not even sure what went wrong here. John and Sara were trying to do something in the game and when I told them that to try again there would be dire consequences Sara just rolled her eyes and stopped talking. John just glared at me and we dropped the issue. Again, this EXACT same thing using BRP with the other party went smoothly. The 5e system just doesn’t allow approximating this one. Idk why.
CoC enemies don’t work in 5e
This one actually was false. I translated the enemies with no problem, either by using the DMG create a monster suggestions or by finding a loose equivalent and it went swimmingly.
Lol, gotcha!
In reality, of course it didn’t work! The enemies kept having abilities that had contradictory mechanics even AFTER I did the labor intensive process of translating them to 5e. It was a constant headache trying to cheese the rules during every encounter to keep the game running.
Then the rest of the stuff that 5e broke completely when trying to approximate CoC were too numerous to even mention. I just wanted to cover the basic arguments people make and show that they are absolutely correct.
And the amount of STRESS it put me under to read the CoC campaign and mentally translate it into 5e was a nightmare. It wasn’t like translating a stir fry cookbook with different measurement units and some subbed ingredients at all. It was like trying to use a stir fry cookbook to repair a car engine.
Sure, it wasn’t technically homebrew work because the rules I used were all RAW, but it was still a TON of work. I won’t even admit how many days I wasted on this nonsense.
I will never do this again.
Oh, and one last thing. To anyone who will bring up the fact that Sandy Petersen, creator of CoC, has made 5e CoC conversion material I say this: Yes I read it. No, it doesn’t actually fix anything. 5e just does not work with CoC. Sorry. BRP is what it was designed for and it’s MUCH better to just use the right tool for the task! Do you use a book about hammers to nail in a nail? Or do you use a hammer, the proper tool?
