I was thinking about making a PC warlock with the Great Old One as a patron. I noticed that under the Great Old One's Book of Shadows, some warlocks could be described as having growing insanity. I think I want him to become increasingly more insane, which would obviously affect one of his ability scores. I have ruled out Strength and Dexterity, which would unlikely be affected; Strength is bodily power, and Dexterity is sneakiness, while these are physical things, and insanity is a mental problem. Constitution is health, which may be related to mental health. Intelligence is memory, which insanity may effect. Wisdom is mental awareness, which insanity may dull. Charisma may be effected, but I am uncertain as to why.

Is Constitution, Charisma, Wisdom, or Intelligence most related to insanity?

  • 10
    \$\begingroup\$ Can you expand on why becoming increasingly insane would "obviously affect one of his ability scores"? That is both: why would it necessarily affect one and why would it affect exactly one? \$\endgroup\$
    – minnmass
    Commented Apr 30, 2023 at 19:45
  • \$\begingroup\$ Something to consider for this - if Intelligence Loss were part of the impact of insanity for Warlocks, that would mean they gradually become less effective Warlocks, which is probably not what you want. \$\endgroup\$
    – Zibbobz
    Commented May 2, 2023 at 12:57

4 Answers 4


Insanity is most related to the Sanity score.

Chapter 9 of the Dungeon Master’s Guide contains optional rules for implementing Sanity as a seventh ability score:

Consider using the Sanity score if your campaign revolves around entities of an utterly alien and unspeakable nature, such as Great Cthulhu, whose powers and minions can shatter a character’s mind.

A character with a high Sanity is level-headed even in the face of bizarre circumstances, while a character with low Sanity is unsteady, breaking easily when confronted by eldritch horrors that are beyond normal reason.

If the character’s degree of sanity is a central feature of your character concept, consider asking your DM to implement those rules for your character: they are there for exactly this sort of character.

Otherwise, the Dungeon Master’s Guide suggests Wisdom.

In the section about Sanity score, we see this instruction:

If you ever need to make a check or saving throw for Honor or Sanity for a monster that lacks the score, you can use Charisma for Honor and Wisdom for Sanity.

So in the absence of a Sanity score, the rules suggests using Wisdom instead.

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    \$\begingroup\$ I would definitely caution mechanising (and this likely trivialising) mental health by putting it behind a stat. \$\endgroup\$ Commented May 1, 2023 at 8:35
  • 4
    \$\begingroup\$ It might be worth adding that one of the official adventure modules uses sanity as a main plot element (Out of the Abyss), and the relevant saves are indeed Wisdom. You could also include the Madness section of the DMG as a result of the failed checks rather than a loss of ability score. \$\endgroup\$ Commented May 1, 2023 at 14:02

There's already an A+ answer.

Thomas Markov's answer is mechanically correct, especially for the GM.

…but, this might still be a bad idea…

That said: as both a player and a GM, I strongly advise caution in trying to bring insanity to your character - mechanically or otherwise - if the campaign doesn't already involve it. While it can be great fun for all involved, it is extraordinarily easy for it to become incredibly painful for everybody else: My Guy Syndrome is lurking in the wings, preparing to leap out and devour the campaign.

Let me expand on that a bit.

At a very basic level, this question is surprisingly similar to "how do I make my character a member of a spaceship crew?".

  • For both questions, there are optional, GM-facing rules if the campaign calls for it (for the this question, as mentioned, the Sanity system; for spaceships, there's a good argument that the Spelljammer book's ships would work).
  • For both questions, there are varying levels of GM buy-in available.
    • For spaceships, the GM could potentially go with anything from "you survived the wreck of a spelljamming ship, but that's the last we'll hear of them" to "we're playing a Spelljammer campaign".
    • For this question, there are options from "just be a little weird at times" to "we're all using the Sanity system".
  • The question assumes a lot about the game world and campaign the GM has in mind - and many answers will force decisions that may or may not make sense within that context.
    • For spaceships, the question implies that there are spaceships flying around the game universe, that some crewmembers are viable adventurers in this world, that this world is interesting to at least some spacefarers, etc..
    • For sanity, well, that goes a little deeper.

You got Sanity in my Sword-and-Sorcery fantasy!

The core meta-game assumption of D&D is that there are several real humans sitting around a table, playing a game together. Those people have agreed to set aside a chunk of time - often a fairly sizable one - to cooperatively tell a heroic story about their characters. The rules seem to be written such that PCs succeed about 65% of the time they roll a d20 and they make it reasonably difficult to accidentally kill a PC: the PCs are the heroes of the story, and will very probably win in the end.

Stories about losing sanity often run counter to this assumption. My experience with Call of Cthulhu is that the story is more about finding the least-bad way of losing than it is about finding a way to win (which in one case involved calling a literal airstrike on our own position as a plan B). The stories were fun to play and re-tell, but they would have been a hard left turn had we come expecting anything more light-hearted.


At its core, D&D is designed around facilitating a sword-and-sorcery fantasy tale. Powerful heroes slay dragons and free princesses; wise wizards foil the plots of evil sorcerers; dashing rogues protect their fellows from fiendish traps and relieve evildoers of their ill-gotten gains.

Focusing on a descent into madness – on a PC's descent into madness - runs afoul of that assumption. That's not to say that it can't be done, but it's not what the system is designed for nor is it what most people are signing up for when they agree to join a campaign.

…that might hit too close to home…

Most portrayals of insanity or mental illnesses in fiction are, generously, "inspired by actual events". If anyone at your table has a mental health concern - or a friend, loved one, etc. who does - focusing on mental heath may very well cause discomfort, hurt feelings, broken friendships.

…and play out poorly.

My Guy Syndrome is the observed problem of a player justifying obviously-bad in-game choices because "that's what my guy would do".

If one player's character has a weak grasp on sanity, it seems reasonable to assume that their choices would be less rational to an outside observer. Thus, the player is more likely to make obviously-bad choices because "that's what my guy would do". This very often leads to broken campaigns and strained friendships: you've come together to play a cooperative game; one player choosing to screw up on purpose isn't fun for the rest of the players.

Note that, by "obviously-bad", I don't mean in a "least-bad" sense or with the benefit of hindsight, but in a "that's clearly a dumb idea" sense. "My Guy Syndrome" has brought us such hits as "I steal the king's crown from atop his head", "my guy will never attack the first round of combat", or even ... shall we just say that "seduction" stopped being the right word a long time ago. Critically, these are all things that the player chooses to do by themselves; if the rest of the players agree, it's almost certainly not My Guy Syndrome.

I could very easily see someone talking themselves into "insanity means randomly selecting a target each round, even from among the other PCs". This may be an extreme example, but it's the kind of trap that "my guy's less than fully sane" can lead to.

So, what do I do?

Talk to your GM and the rest of the players about your concept. If they're hesitant, it's probably best to drop it for this campaign.

If they rest of the players are interested, I would council working with the GM on an "escape hatch" in case something goes off the rails (this could include anything from the character exiting the campaign to a deus ex machina to resolve the insanity). I would also recommend looking more at Firefly/Serenity's River Tam or Psycho's Norman Bates for inspiration than, say, the cast of Alice in Wonderland.

That is to say:

If the GM and the other players don't want a space cadet in their party, well, that just isn't the hill to die on.


Mental health is not a stat.

TL;DR mental health and 'sanity' is not a one dimensional thing that's easily mapped onto a stat or single score.

As a caveat to this answer, I'm playing a Great Old One's Warlock currently, but I've also played a bunch of different games that tried to make sanity or mental health part of the mechanics of the game and not just roleplayed.

The World of Darkness games

Both the 'old' and 'new' each have a system for tracking some sort of 'sanity' stat (humans have Morality/Integrity, more focused on Sins Vs Virtues, and later Integrity more focused on mental well-being and identity), with each flavour of supernatural creature having a different take on it. The systems would have you risk gaining a 'derangement' if you did activities that were opposed to your current 'sanity' score.

The problem with 'Morality' here, and tying it to mental health is both in trivialising the process of worsening mental health or gaining certain psychological conditions, as well as the implication that Character does bad thingCharacter goes mad, because of the existing social stigma around mental health, and the general assumption that mentally unwell people are bad people.

The icing on the cake is then trivialising the difficulties real people have by giving each 'derangement' hard and fast mechanics. It's trivialising because it reduces a very personal set of issues to dice rolling or similar.

Chronicles of Darkness replaces Morality with integrity and immoral behaviour with what is essentially experiencing trauma, but still does it in a dehumanising way. Despite this being a core theme for these games, it's not handled with enough care.

As an aside, The Giant Robot of Offense is a great look into how you might represent anything (including mental health concerns) that may touch on sensitive topics - namely here that you could easily being 'playing' as an insane person in a way that is awfully distressing for someone in your game without realising.


Mouseguard has a stat called Nature, that denotes how close to your mouse like nature you are. Too high/mouselike and you can't function as a member of the guard, too low and you can't function as a mouse (too 'humanlike' although it's not stated that way). This would be trivialising, but it doesn't claim to cover mental health in anyway, but does express a real concern the characters have. Everything else is down to the player to roleplay.

Call of Cthulhu

I've only played one game, and I can't remember which edition. But most of these have a separate track similar to health and treat it like mental health points that can be damaged.

This helps quantify sanity as something that's damaged not something innate to the character themself.

Dungeons and Dragons

As other answers have alluded to, there are rules for sanity presented in the DMG. But these are likely to trivialise mental health and adjacent topics due to how mechanics focused these games tend to be, taking away the human (for lack of a better word) aspect of it.

What I would suggest is, if you're set on showing your character becoming swayed by their patron, and after reading the other answers and discussing with your other players (of which the GM is one) if they would be comfortable with you deliberately not rolling or failing some rolls that you think might be impacted by your close association with the patron. If it's not something that needs rolling though, you can just roleplay it.

Maybe you don't notice something otherworldly because to it it's normal (wisdom based perception) or you try to be charming and persuasive but you being up otherworldly topics instead of every day ones.

This way, it's a social agreement that it's important for you to express this aspect of your character, and you need buy-in from the players that it might have a mechanical impact without having to reduce it to a one dimensional track.


Wisdom, or possibly Intelligence.

In the Dungeon Master’s Guide (p. 264), in the section on new ability scores it mentions making a Wisdom saving throw for a Sanity check.

However, there is another option which we tried in our campaign. We changed it and used Intelligence as the ability to do Sanity checks. This was based on a player's pointing out that the 8th-level spell Feeblemind (Player’s Handbook, p.239) requires an Intelligence saving throw. The spell blasts "the mind of a creature [...] attempting to shatter its intellect and personality." In this powerful -sometimes devastating - spell, there is a clear link between the Intelligence stat and being susceptible to insanity.

We play-tested it throughout a homebrewed horror campaign and it worked well.

I guess the other thing to consider is whether Charisma could play a role in checks against Insanity in some way. For example, if a player with a high Charisma score wanted to help a fellow fellow PC by helping them remain calm and stable in the face of something horrific, I might allow the PC who is horror-struck to add the assisting PC's Charisma modifier onto the saving throw. I'd allow this at my table based on the similar effect of the Calm Emotions spell (PHB, p.221).

In the end it will be up to the DM to decide but these are the options I would consider.

  • \$\begingroup\$ I feel like shattering intellect and personality via feeblemind isn't related to sanity. Otherwise you couldn't have mad scientists or wizards because they would not have the intellect to be a scientist or wizard anymore. Also, insane people have a lot of personality. Feeblemind seems to make someone more like a husk of themselves rather than insane. \$\endgroup\$
    – IT Alex
    Commented May 11, 2023 at 16:46

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