Homebrew Sanity Mechanic

[George_Smith]

My group has asked me to run a Cthulhian horror/Call of Cthulhu game in 5th Edition. As such, I want to try to create a sanity mechanic other than what's present in the DMG, as I want more of a sliding scale than just “You're Insane.”
I'm basing this in part off of a poorly remembered game of Call of Cthulhu, so it may not be entirely appropriate. As such, any comments or advice is appreciated.

One thing that I seem to remember is that magic in Call of Cthulhu was something granted by the Elder Gods, and the more you used it, the more sanity you would lose. As such, it seems that a low magic setting would be more appropriate than a high magic one. Adding to that is the fact that three of the five players are relatively new to tabletop rpgs, and I'd like to avoid overwhelming them with magical options.

So. The thought I'm currently working with is a scale of Sanity from 0 to 100, with 100 being the sanest people in the world, who can rationalize away anything supernatural. There are not many people at this level of Sanity. Most people are between 95-97, reflecting some superstitions, but they haven't been presented with the horror of reality yet.

Now, you may be asking 'How does this result in a lower magic setting?', and that is a good question. You see, I'm planning on having spells cost an amount of Sanity equal to their spell level, though each spell level only drains down to 100-(SL*10) Sanity. So a 1st level spell will drain you down to 90 Sanity if you cast enough of them, but no further as your mind has warped enough to comprehend, or at least, not be further damaged by the spell.

The closest analogue to Cthulhian monsters that I can think of is Aberrations, so those are going to be a primary enemy, with a chance to cause Sanity loss equal to their CR when they're encountered, again, not causing Sanity loss at a point equal to 100-(CR*10). This does mean that some monsters will be able to cause Sanity to hit negative levels, but such is life.

So now you may be asking “How does this impact gameplay”. I'm not 100% sure on that yet. I'm thinking it'll have a chance to cause them to suffer from the effects of a short term madness, based on their Sanity level. I was thinking of treating the Sanity level as the chance to resist madness on a d100 roll, aiming to roll under your Sanity level, with the check triggered every time you encounter or do something that would cause you to lose Sanity. This does mean that spellcasters have an inherently higher chance of failing if they've been casting spells, but as that means they've been calling upon the power of Elder Gods, even unknowingly, I feel like that's a fair trade. Given how incapacitating some of the Short-Term Madness effects can be, I'm going to be shortening the effects to a number of rounds equal to the degrees of failure. So if their Sanity is 50, and they roll a 75, that's 3 Degrees of failure – one for each 10 points they failed by, rounded up, thus, their Short-Term Madness lasts 3 rounds.

Recovering Sanity is a hard part. I don't want it to be too easy to recover Sanity, but I don't want it to be too hard either. I'm thinking that they can recover Sanity in sanitariums or similar places, with stays restoring 1d4+(Days Stayed) Sanity. So if they commit themselves for a month, they'll recover between 31 and 34 Sanity. This isn't very realistic, but they're adventurers. They're made of sturdier stuff than the average person.

I'm also going to be incorporating a method of gaining temporary Sanity Points, through the use of alcohol, opiates, and similar substances that cloud your mind, as this keeps you from realizing the full horror of what you're confronting or doing. These will be rated on a point scale of 0-5, with players able to absorb as many points as their Constitution Modifier before passing out. Using these substances will provide temporary Sanity points equal to 5 or 10 times the point rating of the substance. Probably 10, so as to not end up with decimals if an item is rated at .5 points or the like, though rounding up is an option as well.

If they drop to or below 0 Sanity, then they become permanently insane, suffering a permanent Long-Term or Indefinite Madness until cured by being committed to a sanitarium for at least a month. Exclusions may apply to the options on the tables.

That's about all I've got at the moment, I'd appreciate any feedback.

[TurboGhast]

This is a cool system. However, SAN loss seems maybe a little too instant. Perhaps creature-based SAN loss is at a rate of 1 per turn, and maxes at their CR.

[George_Smith]

That could work.
I had been thinking of exposure as a sudden shock, perhaps with a wisdom saving throw to try to fit it into your worldview to reduce SAN loss to half, rounded down, but giving them the save at the beginning, and letting that determine how many rounds of SAN damage they take over the course of the exposure would probably work better. It fits into the mechanic better than sharp sudden losses, because if they kill a creature before it exposes its nature too much, it stands to reason that they wouldn't take SAN damage unless they went and inspected it further. Perhaps that's when they'll take flat damage = CR, Save Half or Negates.

[Once a Fool]

I think sanity in a game works best if it represents a buffer from psychotic breaks. Whatever your mechanic for losing it, once drained, a character can temporarily lose control (and their grip on reality) without being removed permanently from play.

As things calm down, the sanity can return, but it is always only a veneer holding the next psychotic break at bay. If you've ever played the old GameCube game, Eternal Darkness (a very Cthulu-mythos-inspired game), that's basically how they handled sanity loss.

[dysike]

As someone who really likes cosmic horror in general and shares your dislike of sanity systems which are basically just a second HP value I have a couple suggestions.

Firstly I like what ToC did where it tied sanity to your character's beliefs and motivations, essentially your character had a motivations and three beliefs, if any of the beliefs where dis-proven or your motivation was shown to be pointless you took a lot of sanity damage, it also worked the other way where if you take too much san damage one of your beliefs can be destroyed then as well, it's a good representation of how the things the characters have experienced have affected them.

Secondly have a good think about how you want to represent any mental problems accrued by the characters, in horror it's always better to scare the players than the character so the system should be that. Personally I'd go with effects which result in loss of control of your character, like having a character who's developed a split personality occasionally black out and find out they've lost a few hours, you can also use characters with delusions or hallucinations to great effect by describing what they see and hear, not necessarily what actually happens.

Personally I think D&D is a great system for cosmic horror, the setting by definition has a large number of incredibly powerful beings all fighting for their own goals. Whenever I need horror campaign ideas I just think about what being a normal commoner in any D&D setting must be like.

Hope this helps.

[ThermalSlapShot]

A friend did something with sanity but made it another ability score.

Sanity was equal to Hit Dice (physically resistant/Luck/Whatever) + Sanity Modifier.

Sanity Score went from 8 to 20 like a normal score and was made as the DMG suggest for new ability scores.

Every OC gains a +2 sanity for being heroes.

So while some monsters did HP damage some did a combination of HP and SP (Sanity Points) damage. Some monsters abilities and Spells only do SP damage.

Psychic damage and spells like Phantasmal Force screw with a person's sanity and not their HP.

[Slipperychicken]

Have you tried looking at existing sanity mechanics? I haven't played CoC, but I know there was a sanity variant for 3.5 (http://www.d20srd.org/srd/variant/campaigns/sanity.htm), and the 5e DMG features some sanity and madness variants.

I would consider making it more flexible, allowing characters to both save against SAN loss (including that from spellcasting), and get the equivalent of "death saving throws" when they hit 0 SAN. Perhaps characters could grow accustomed to some horrors over time, getting advantage on saves (or d100 rolls) against a horror after successfully saving against it three times.

For ways to recover sanity, I think that PCs could try to help each other work through it. For a first attempt at a houserule: Characters could attempt therapy on each other over the course of a week, reassuring each other and trying to making sense of the madness, which would most likely be a charisma check, DC 15 or 20. A success would probably improve sanity by 1d4 points, 2d4 on a natural 20, or reduce sanity by 1d4 on a natural 1. Using drugs and herbs to help treatment might be a wisdom(medicine) check DC 15, with success granting advantage on the therapy roll, and failure imposing disadvantage. Successfully completing a major quest or adventure (or a comparable achievement) might also improve sanity by 1d4 or more, depending on how heartening the success is.

Also, I'm not sure if 5e is the right system for horror. Almost all of its mechanics revolve around the players performing magical wonders and engaging in heroic fantasy combat, which is not suitable for evoking the feelings of helplessness or existential dread which are characteristic of Lovecraft's work. It's hard to be spooked by ghouls and dark places when you're literally a conduit of divine power, throwing miracles from your fingertips and bursting with holy light to banish the evil.

[Lolzyking]

I'd recommend keeping the sanity of the players private from them, sure let them know how much they each start with, but don't let them know how insane they are going, just describe things to them like, as you walk into the room x character sees y in the corner of his eyes. Tell them something ran past them an ask them to make an opportunity attack, sometimes it might be an enemy, it might not, and sometimes they might commit friendly fire.

I ran sanity like this for a hypercube style dungeon, I told the players to bring a stack of sticky notes whenever they failed a roll to keep their sanity, they'd either progress x rooms at my choice until they rolled to recover, or I took their current notes, or I tell them they are no longer aware of which doors are nswe.

[George_Smith]

Have you tried looking at existing sanity mechanics? I haven't played CoC, but I know there was a sanity variant for 3.5 (http://www.d20srd.org/srd/variant/campaigns/sanity.htm), and the 5e DMG features some sanity and madness variants.

I would consider making it more flexible, allowing characters to both save against SAN loss (including that from spellcasting), and get the equivalent of "death saving throws" when they hit 0 SAN. Perhaps characters could grow accustomed to some horrors over time, getting advantage on saves (or d100 rolls) against a horror after successfully saving against it three times.


I hadn't looked at the 3.5 sanity mechanics, but it does seem pretty similar to what I've worked up here, just with different sanity losses -- more random -- and each person has a different starting sanity. I would like to keep the losses and starting sanity as simple as possible, since I do have a number of players who are new to tabletop rpgs in general, and I don't want to overwhelm them with this.



For ways to recover sanity, I think that PCs could try to help each other work through it. For a first attempt at a houserule: Characters could attempt therapy on each other over the course of a week, reassuring each other and trying to making sense of the madness, which would most likely be a charisma check, DC 15 or 20. A success would probably improve sanity by 1d4 points, 2d4 on a natural 20, or reduce sanity by 1d4 on a natural 1. Using drugs and herbs to help treatment might be a wisdom(medicine) check DC 15, with success granting advantage on the therapy roll, and failure imposing disadvantage. Successfully completing a major quest or adventure (or a comparable achievement) might also improve sanity by 1d4 or more, depending on how heartening the success is.


I do like this, as it gives the players the ability to increase sanity without resorting to sanitariums if they choose. I'd probably make it 1d6 for each week -- it's not quite as effective as the trained help would be.



Also, I'm not sure if 5e is the right system for horror. Almost all of its mechanics revolve around the players performing magical wonders and engaging in heroic fantasy combat, which is not suitable for evoking the feelings of helplessness or existential dread which are characteristic of Lovecraft's work. It's hard to be spooked by ghouls and dark places when you're literally a conduit of divine power, throwing miracles from your fingertips and bursting with holy light to banish the evil.

I didn't express it clearly in the original post, but one of the things I'm changing is that there are no conduits of divine or arcane power. All magic, regardless of how it's regarded, is derived from a single source -- the Great Old Ones. As such, magicians are uncommon, magic is uncommon, and magic items are, you've guessed it, uncommon. The only creatures that can use magic without suffering sanity loss would be aberrations, the creatures of the elder gods, because most of it involves chanting in the language of the Great Old Ones -- in this case, Deep Speech. Each spell list remains its own separate list, but I'll allow any spellcaster to pull from any list if they can justify it to me -- maybe they acquired a rare scroll detailing the invocations and gestures needed to manifest the power. Maybe they had a psychotic break and saw into the heart of the universe or the mind of an aberration, learning a new spell.

On the subject of magic items, I think I might make them involve sanity loss as well. If they're one shot items, sanity loss equal to the spell level involved in making it, half on a successful save, and you'd be immune to san loss if your sanity is low enough as with the casting of spells. For permanent magic items, maybe a cost of 1 san, negated on a save, each time its used, no san loss if below 50 san.


I'd recommend keeping the sanity of the players private from them, sure let them know how much they each start with, but don't let them know how insane they are going, just describe things to them like, as you walk into the room x character sees y in the corner of his eyes. Tell them something ran past them an ask them to make an opportunity attack, sometimes it might be an enemy, it might not, and sometimes they might commit friendly fire.

This is an interesting idea. I'd rather not keep the sanity scores from the players, because of how many new players I have -- I'd like to keep the game mechanics as transparent as possible -- but I do like the idea of creeping insanity, where they're not sure if they're attacking friend or foe, or anything at all, as a minor event that happens more frequently as they grow more insane.

[Kajorma]

I really like all of this, and it makes me want to run a game with these rules.

One thing I find concerning though:

I didn't express it clearly in the original post, but one of the things I'm changing is that there are no conduits of divine or arcane power. All magic, regardless of how it's regarded, is derived from a single source -- the Great Old Ones. As such, magicians are uncommon, magic is uncommon, and magic items are, you've guessed it, uncommon.

I've tried to do things like that before (not this edition). The game is balanced with magic items in mind.
This can lead to problems with ECL, and having some classes just being far and away, flat out better than others.
Your sanity mechanic is a nerf on spellcasting, and your lack of magical items is a nerf on melee types.

None of this is bad, per se, but it can make things challenging while trying to run an enjoyable game.

You could limit playable classes to Barbarian, Fighter, Rogue and Monk (disallowing the magic paths) to try and keep your players on par with each other. You'd still have to worry about balancing encounters against the group.

It looks like, by this system, cantrips would cause no sanity loss. I don't know if that's by design, but if you *do* have a spell slinger in the group, that will make for some very interesting dynamics with people who reject the idea of the supernatural.

At any rate, it looks like it will be fun for the players, but a lot of work for you. Definitely keep us posted on how it goes, and what tweaks you made over the course of play. I'd like to see what the system looks like after playtesting.

[George_Smith]

I really like all of this, and it makes me want to run a game with these rules.

One thing I find concerning though:


I've tried to do things like that before (not this edition). The game is balanced with magic items in mind.
This can lead to problems with ECL, and having some classes just being far and away, flat out better than others.
Your sanity mechanic is a nerf on spellcasting, and your lack of magical items is a nerf on melee types.

None of this is bad, per se, but it can make things challenging while trying to run an enjoyable game.


To my knowledge, 5e is based much less around the need for magic items, but you're right. I'll probably take the Sanity point loss off of permanent magical items like +1 weapons/armor and off of potions, but leave it on for things like wands, and the expendable items like scrolls.



You could limit playable classes to Barbarian, Fighter, Rogue and Monk (disallowing the magic paths) to try and keep your players on par with each other. You'd still have to worry about balancing encounters against the group.

It looks like, by this system, cantrips would cause no sanity loss. I don't know if that's by design, but if you *do* have a spell slinger in the group, that will make for some very interesting dynamics with people who reject the idea of the supernatural.

At any rate, it looks like it will be fun for the players, but a lot of work for you. Definitely keep us posted on how it goes, and what tweaks you made over the course of play. I'd like to see what the system looks like after playtesting.


I do know that one player is intending to play a Cleric, so I'll certainly have some feedback for how it works on spellcasters. Cantrips cost sanity loss down to 95 Sanity, so they basically don't cause a loss of sanity for casters, which I think is fair, since it's essentially their version of a basic attack.

[Estrillian]

You might want to consider making Warlocks the only spell casting class (although I can see some argument for Bards re-skinned as Priests). They already derive their powers from dark pacts, and they are thematically exactly set up for losing their minds (and souls) as they gain invocations and powers.

Your Sanity system does sound an awful lot like Call of Cthulhu, which isn't a bad idea. In CoC you have a Sanity score (0-100) and exposure to horrifying situations makes you lose Sanity. If you lose too much in one go you suffer temporary or long-term insanity. Temporary insanity are things like hallucinations, blackouts, fits, running away, curling up in a ball, temporary amnesia and so forth. Long term insanity, which come from bigger losses, are more traditional (for fantasy games) things, phobias, phillias, voices in the head and so on. You can recover from either, but your Sanity is lower so you are closer to a total collapse. An important mechanic is that the more you know about the Cthulhu mythos (the higher your Mythos Lore) the less sane you can be, in that your max sanity is 100-lore.

I would second the idea that Trail of Cthulhu introduces though. In that you have stability, which is a hit-point like pool of resistance to minor shocks and fear. When you run out of stability you take more serious consequences, a little like the way you start taking death saving throws (or long term injuries if you use those optional rules) when you run out of physical hit points. You also have things called Pillars of Stability, things like your family life, or your trust in authority, or your belief in the law, which you can use to try and restore stability, and which can be shattered by a big enough shock, leaving your maximum stability destroyed.

You could have a system where a players has sanity hit dice of some sort, which give a sanity score. Aberrations do sanity damage just by existing. If you fall to 0 sanity you go mad. You could then spend sanity dice to try and restore sanity (like stability), or have the risk of losing them to sanity damage inflicted when you are on 0 sanity. Alternatively do this like the DMG suggests, add a stability attribute, take attribute damage from aberrations, maybe making stability saving throws to try and halve?