Homebrew monster: how to create a weak spot

[Eric Diaz]

I am writing homebrew monsters for 5e based on Brazilian mythology.

Some of them have various resistances and immunities but also weak spots (especially on the belly button).

How would you do that in 5e? I've created and modified quite a few 5e monsters, but don't remember this exact situation.

Is there any precedent on what we can use? Higher AC? Disadvantage? Needs a critical hit?

Another problem is that the weak spots are not necessarily know by the PCs, it would be cool if they could hit it by accident, but not strictly necessary.

I'd appreciate any existing examples.

Thanks!

[Anymage]

D&D is hard pressed to do weak spots on a target, and 5e is doubly so because it compiled all the fiddly little numbers under flat advantage/disadvantage. Plus, there's practically no player skill involved in either knowing the weak points (aside from either doing your info gathering before the fight or memorizing the mythology/monster stat blocks ahead of time), or actually targeting them once the information is known.

Zombies have undead fortitude and vampires have gaseous form upon death. The former might be a way to show a monster that just keeps going unless you either know its weak point or manage to bring enough brute force to overwhelm it. The latter might be something to use similarly if you want a long term antagonist. You can do enough damage to drive it away, but unless you know its weakness you can only knock it out/drive it off by removing all its hit points. Only by knowing its specific weakness and applying it (either on the hit that drops the monster to 0 or afterwards if you can have the monster down but recuperating) can you actually kill the thing.

[GalacticAxekick]

I think 5e OS an awesome system for weak spots. Have a look at some of my homebrew monsters (https://homebrewery.naturalcrit.com/share/_FCM0bfXJ).

The simplest way to represent a weak point is to make a monster EXTREMELY difficult to damage until a condition is met.

For my dragons, this comes in the form of Invulnerable Hide & Soft Underbelly (which raise the dragon's AC far above 20 and give it rogue-like Evasion, UNLESS you attack the dragon from beneath.)

For my giants, this comes in the form of Elevated Weak Point (which causes any attacks that reach below the giant's waist to deal 1 damage, forcing you to either climb higher or knock it prone).

Tell me more about your monsters and we can brainstorm weaknesses.

[Twelvetrees]

The main method existing monsters have for weak spots is via vulnerability to a specific damage type.

Treants (https://www.dndbeyond.com/monsters/treant) are vulnerable to fire, skeletons (https://www.dndbeyond.com/monsters/skeleton) are vulnerable to bludgeoning, and so on.

If you want something closer to a weakness in a certain part of the body, vampires (https://www.dndbeyond.com/monsters/vampire) have a list of specific weaknesses that you could draw on for inspiration.

[Eric Diaz]

D&D is hard pressed to do weak spots on a target, and 5e is doubly so because it compiled all the fiddly little numbers under flat advantage/disadvantage. Plus, there's practically no player skill involved in either knowing the weak points (aside from either doing your info gathering before the fight or memorizing the mythology/monster stat blocks ahead of time), or actually targeting them once the information is known.

Zombies have undead fortitude and vampires have gaseous form upon death. The former might be a way to show a monster that just keeps going unless you either know its weak point or manage to bring enough brute force to overwhelm it. The latter might be something to use similarly if you want a long term antagonist. You can do enough damage to drive it away, but unless you know its weakness you can only knock it out/drive it off by removing all its hit points. Only by knowing its specific weakness and applying it (either on the hit that drops the monster to 0 or afterwards if you can have the monster down but recuperating) can you actually kill the thing.

Thanks! This is a good idea. The monster I'm creating has nigh-invunerable skin, so maybe not this specific monster, but it is something to keep in mind.


I think 5e OS an awesome system for weak spots. Have a look at some of my homebrew monsters (https://homebrewery.naturalcrit.com/share/_FCM0bfXJ).

The simplest way to represent a weak point is to make a monster EXTREMELY difficult to damage until a condition is met.

For my dragons, this comes in the form of Invulnerable Hide & Soft Underbelly (which raise the dragon's AC far above 20 and give it rogue-like Evasion, UNLESS you attack the dragon from beneath.)

For my giants, this comes in the form of Elevated Weak Point (which causes any attacks that reach below the giant's waist to deal 1 damage, forcing you to either climb higher or knock it prone).

Tell me more about your monsters and we can brainstorm weaknesses.

These are both interesting ideas! For my monster, a higher AC might work better (looks like a erewolf, nigh-invunerable skin, weak belly button).

I was curious on HOW to add his to the monster stats, since I don't remember any "official" monster with a similar weakness.

The first monster I'm doing is the Capelobo (https://www.google.com/search?q=Capelobo&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjCp46fhdfyAhUgI7kGHblrDbwQ_AUoAXoECAEQA w&biw=1608&bih=880):

Capelobos are fearsome, murderous creatures that roam the forests at night. The walk upright on two big hooves that leave circular tracks. Their heads resemble those of anteaters. Their bodies are hairy and strong, and they claws are remarkably long and sharp.

Hatred for humanity. [...] kill for sport [...] terrorize their victims [...]

Curious diet. A capelobo enjoys eating kittens and puppies more than anything, which brings them out of the woods and to prowl around human settlements. When it kills bigger game, including cattle and humanoids, it trepanates its prey in order to suck the entirety of the encephalic mass. The victims are easily recognizable by a round hole in the empty skull. Some capelobos also like to drink the blood of their victims, dead or alive.

Uncertain origins. It is uncertain what curse, ritual or accident of nature created such monsters. Rumor has it that in certain tribes, the elder can become capelobos with time. However, nobody can tell for sure if this transformation is natural, willful, or even reversible.

[Eric Diaz]

Okay, one idea that might work: call it three quarters cover.

A different AC for the belly would work very similarly, but three quarters cover at least exists in the game.

A bit worried that this will give sharpshooters EVEN MORE power, but people who use the feature as written will probably see no problem with that.


The main method existing monsters have for weak spots is via vulnerability to a specific damage type.

Treants (https://www.dndbeyond.com/monsters/treant) are vulnerable to fire, skeletons (https://www.dndbeyond.com/monsters/skeleton) are vulnerable to bludgeoning, and so on.

If you want something closer to a weakness in a certain part of the body, vampires (https://www.dndbeyond.com/monsters/vampire) have a list of specific weaknesses that you could draw on for inspiration.

Vampires have some interesting weakness... might be appropriate to this blood-scuking creature. Will check!

[Eric Diaz]

On a second thought... "A target with three-quarters cover has a +5 bonus to AC and Dexterity saving throws."... so would it have a different saving throw against a fireball? I dislike the idea...

Any opinions?

Here are two versions:

• Soft belly: The capelobo’s belly button does not have any resistances or immunities. Treat it as a target with three-quarters cover; the attacker must declare its intention to hit the spot. Attack rolls that are equal or higher than the capelobo's AC hit the creature elsewhere even if they are not high enough to hit the belly button.

• Soft belly: The capelobo’s belly button does not have any resistances or immunities. Treat it as a target with AC 20; the attacker must declare its intention to hit the spot. Attack rolls that are equal or higher than the capelobo's AC (15) but lower than the belly button (20) hit the creature elsewhere.

Another option: knowing about the capelobo's weak spot gives the target advantage. This is less than ideal for several reasons - it wouldn't work against immunity, for example - but again it is at least a mechanic that exists in the game.

[BerzerkerUnit]

I have ruminated on this concept before and here's my preference:

"A weak point represents a particular vulnerability a creature has, like Smaug's missing scale, a vampire's cardiac allergy to wooden stakes, etc. Damage dealt to a creature through its weak point triggers the Stunned, Paralyzed, or Unconscious condition or is doubled. Such creatures are usually aware of such weaknesses or will be after an initial strike, however they have little recourse other than to flee foes that have proven aware of it or engage in tactics to cover for said weakness (the heart of a vampire in full plate will be impossibly hard to pierce with a wooden stake).

To strike a creature's weak point, a player must have Advantage on the attack roll. They sacrifice this advantage to make the attempt, rendering the attack vulnerable to disadvantage from other sources. Only one such attempt can be made each turn. Legendary creatures may expend a use of their Legendary resistance to avoid a condition applied in this way."

That's my fix when it's relevant.

[GalacticAxekick]

These are both interesting ideas! For my monster, a higher AC might work better (looks like a werewolf, nigh-invunerable skin, weak belly button).

I was curious on HOW to add his to the monster stats, since I don't remember any "official" monster with a similar weakness.

The first monster I'm doing is the Capelobo (https://www.google.com/search?q=Capelobo&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjCp46fhdfyAhUgI7kGHblrDbwQ_AUoAXoECAEQA w&biw=1608&bih=880)Give it ridiculous AC and Invulnerable Hide, just like my dragons.

Instead of Soft Underbelly, give it vulnerability to piercing weapons and a feature called Miniscule Weak Point, which has the following description:

"The capelobo carefully guards its soft bellybutton while it is mobile. When the capelobo is immobilized (e.g. when it is grappled, restrained, or incapacitated) creatures aware of this weakness treat its AC as 10, and it does not benefit from Invulnerable Hide."

[Eric Diaz]

I have ruminated on this concept before and here's my preference:

"A weak point represents a particular vulnerability a creature has, like Smaug's missing scale, a vampire's cardiac allergy to wooden stakes, etc. Damage dealt to a creature through its weak point triggers the Stunned, Paralyzed, or Unconscious condition or is doubled. Such creatures are usually aware of such weaknesses or will be after an initial strike, however they have little recourse other than to flee foes that have proven aware of it or engage in tactics to cover for said weakness (the heart of a vampire in full plate will be impossibly hard to pierce with a wooden stake).

To strike a creature's weak point, a player must have Advantage on the attack roll. They sacrifice this advantage to make the attempt, rendering the attack vulnerable to disadvantage from other sources. Only one such attempt can be made each turn. Legendary creatures may expend a use of their Legendary resistance to avoid a condition applied in this way."

That's my fix when it's relevant.

That's interesting, has lots of uses. Thanks!


Give it ridiculous AC and Invulnerable Hide, just like my dragons.

Instead of Soft Underbelly, give it vulnerability to piercing weapons and a feature called Miniscule Weak Point, which has the following description:

"The capelobo carefully guards its soft bellybutton while it is mobile. When the capelobo is immobilized (e.g. when it is grappled, restrained, or incapacitated) creatures aware of this weakness treat its AC as 10, and it does not benefit from Invulnerable Hide."


Yup, that sounds great! I like the idea of the spot being easy to hit if the capelobo is incapacitated etc.

[Bohandas]

high damage reduction that is bypassed by critical hits

[Yakk]

So you want a weak spot.

What story do you want to tell with this weak spot?

1. The relatively unique creature is a tough fight, and they are finally killed by hitting it.

This is just high HP. You narrate the hit on the weak spot as the kill.

2. The creature is a puzzle monster, where PCs first encounter it as something very difficult, and when they solve the puzzle the creature becomes weaker.

Here you'll have some "if you target X, you get Y benefit" mechanics.

3. The creature requires a lucky blow to take it out.

A creature that is vulnerable to critical hits. This can be combined with either of the above systems.

All 3 of these (independently) can evoke "a weak spot", but play very differently.

[BerzerkerUnit]

I just had a high level game use my “technical crit” rules. Beating AC by 5 is maximum damage. Worked great.

This diminishes dependence on GWM and Sharpshooter, balances martials better against high level casters whose save based spells get no such benefit.

[JNAProductions]

I just had a high level game use my “technical crit” rules. Beating AC by 5 is maximum damage. Worked great.

This diminishes dependence on GWM and Sharpshooter, balances martials better against high level casters whose save based spells get no such benefit.

That sounds really risky with Smites.

Assuming a foe who's hit on a 10+, that means that on a 15+ you get max damage on a Smite, that can be...

11th Level Paladin who attacks with a 1d8 weapon and has +4 Strength/Dexterity as appropriate. 1d8 (Weapon)+1d8 (Improved Divine Smite)+4d8 (3rd Level Smite)+4 (Stat Modifier) for 52 damage at the cost of one third level slot, 30% of the time.
Of that 30%, one in six will be a crit. Which doubles everything but the 4 static damage, for a total of 100 damage on the nose.

[Corey]

It seems like there's a consensus, along the lines:

(Assuming the opponent knows the weakness, which seems likely)
A successful Aimed Strike goes against much lower AC than other hits.
An Aimed Strike has disadvantage and/or other penalties.
An Aimed Strike becomes much easier under certain circumstances (e.g. immobilization, which also supports auto-critting).

[BerzerkerUnit]

That sounds really risky with Smites.

Assuming a foe who's hit on a 10+, that means that on a 15+ you get max damage on a Smite, that can be...

11th Level Paladin who attacks with a 1d8 weapon and has +4 Strength/Dexterity as appropriate. 1d8 (Weapon)+1d8 (Improved Divine Smite)+4d8 (3rd Level Smite)+4 (Stat Modifier) for 52 damage at the cost of one third level slot, 30% of the time.
Of that 30%, one in six will be a crit. Which doubles everything but the 4 static damage, for a total of 100 damage on the nose.

I've been using Heroic Crit rules for a long time (a crit is maximum base damage and a roll of base damage instead of just 2 rolls of base damage). I like crits to be meaningful, they remain so, particularly for a character type that depends so much on a few heavy blows. Crits are unmodified, but the technical crits greatly speed up combat and at a high level game, that's a massive + and rogues truly love them.

At the end of the day, if I feel a combat has swung to heavily in the party's favor (a string of good rolls making this have more impact than I like), I can just tweak enemy HP behind the screen, or add a few mobs. The players feel stronger, and some (that take forever to do basic math in front of others) feel better over all, more of the time.

But that's me. I know a lot of DMs don't like to improvise or tweak on the fly, and some seem to take fiendish glee in seeing players fail, or their efforts be ground down to a predictable statistical norm that may serve their style better. All I can say is this worked exceptionally well for me and my players and was demonstrably more fun and faster than the default.

[Yakk]

I mean, if monster HP don't matter because you change how many HP a monster has on the fly, then yes, anything you do with changing how damage works has no impact on the game. The damage an attack does becomes a matter of fluff and flavor.

I get how that works, but it really does change how you view damage.

[BerzerkerUnit]

I mean, if monster HP don't matter because you change how many HP a monster has on the fly, then yes, anything you do with changing how damage works has no impact on the game. The damage an attack does becomes a matter of fluff and flavor.

I get how that works, but it really does change how you view damage.

I think your tone speaks to an inference I'd disagree with. It's really more about how you view balance (encompassing damage as element of balance). If you chase balance in house rule, adventure, and class design too far, you find yourself eliminating more and more options and concepts, banning builds and combinations endlessly bc the monk is a class people play. Letting your imagination loose and then whittling down is an approach. Depending on your goal, it might be the right one. I don't like my DnD grounded to low, so it won't be for me.

In general though, I prefer to see balance as something that you target during design, but that you don't allow to be a shackle. I've seen a lot of critiques on this board and others that a class or subclass is too good bc it's better than X in the PHB, even though it's mechanically inferior to half the preferred MC builds optimizers enjoy like sorcadin, SADboys, etc. Same for houserules, a lot of work to nerf casters instead of boosting martials (like this does).

The other end of balance is done during play. If you rigidly adhere to monster statblocks bc "I did the CR and encounter math dammit, and the players should win or lose based on dice and decisions!" That's totally fine. I run that way most of the time myself. But I'd never let the fated encounter of a player with their nemesis or the true final boss (or secret boss they worked to find) in a campaign be overcome by some lucky rolls, so I'd definitely scale hp up in those instances (unless having them trip on their **** in the duel or anticlimactic battle better serves their role in the story).

[Segev]

Here's my suggestion for something like this. Mix and match as needed for various sizes of weak spot and vulnerabilities to not being hit there.

Only Vulnerable In One Spot: The creature's hp represent its efforts to protect that weak spot, right up until the last one (which is lost when the weak spot is hit and the creature dies). The creature cannot be reduced below 1 hp by any blow that does not strike the weak spot. The weak spot has +5 AC (or more, or less, depending on how big the weak spot is) over the rest of the creature. It can be deliberately targeted, and any critical hit that could reduce the creature to 0 hp is considered to have hit the weak spot. Describe critical hits that don't reduce it to 0 hp as being very near the weak spot or as being desperately blocking the attack that would have hit the weak spot.

Invulnerable Backside: A step up on the "only vulnerable in one spot," this variant adds some puzzle qualities and directionality. Each round, at the end of its turn, choose a direction from which the monster cannot be harmed. It is treated as having total cover from that direction. Once the party realizes it takes no damage when hit from this direction, it should be easy to determine what direction that is. (e.g. "you can't hurt it when its back is to you, and you can tell it's facing towards the east right now.") This can be used in conjunction with Only Vulnerable In One Spot, or it could be that its "weak spot" is the whole side that isn't protected, in which case it's fought normally from the "weak side."

Nigh-Invulnerable; Soft Underbelly: The creature has resistance to all damage, except against critical hits (which should be described as hitting it in its soft underbelly) or against damage dealt by creatures that spend a bonus action aiming for its soft underbelly. The Help action can be used to allow the beneficiary to aim for the soft underbelly without having to spend a bonus action.

Protected Weak Point: The creature is aware of its vulnerable part, and has paws or a shell or something it can use to actively protect it. As a reaction, it can negate one source of damage entirely, unless the damage source's player specifically and correctly calls out the weak point and declares they're aiming for it, in which case this only provides a +5 to AC as a reaction.