Can characters/NPCs understand what a crit (Nat 20) is? If so, can they tell that Adamantine Armor negates crits?

Context: I'm trying to figure out if there's any good reason Tier 4 PCs wouldn't bring Adamantine Armor with them when using Astral Projection.


6 Answers 6


The characters know that certain hits hit harder than others.

There is no real backup to this, critical hits are entirely a game term. There is no evidence behind characters knowing game terms, because that would be metagaming (as referenced in other similar questions, already linked in the comments).

However, it's undeniable that some hits do in fact hit harder than others. In my experience, this is usually explained by a skillful hit, like finding a small chink in someone's armor and managing to get a good stab in - a difficult feat that requires a bit of luck. Another example would be getting everything right: posture, form, breath out when swinging down, etc. Something that can be hard to accomplish in the heat of battle when someone else is throwing fire at you, but can certainly give you the upper hand.

As far as explaining how Adamantine Armor prevents that, it's magic. There are no flaws in the armor to exploit, thanks to magic. And, because of this magic, the protection extends to your already neigh-uncut-able silver cord even further, preventing just about anything from cutting it -- even a Githyanki Knight's silver longsword, which required the knight to get lucky and perform some maneuvers to get behind you to even get the chance to slice it (to get a critical hit).

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    \$\begingroup\$ @ThomasMarkov To be fair, multiple earlier editions did include explicitly non-magical items in their magic item lists, adamantine armour among them. \$\endgroup\$
    – GMJoe
    Commented Feb 9 at 23:14
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    \$\begingroup\$ @ThomasMarkov Indeed, in this case I have been undone by my memory of first/second edition. SAC's litmus test has as its first question, "Is it a magic item?" and yes, in 5e it is. Interestingly, its description (which I did read before posting) does not say it is magical. \$\endgroup\$
    – Kirt
    Commented Feb 9 at 23:58
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    \$\begingroup\$ It's an interesting thing about luck. The better your armor is, the less likely they are to hit you. But when they do hit you, the more likely it is to be one of these 'lucky shots' that really hurts. If your armor is good enough, they can't land normal blows - only extra-hurtful blows! \$\endgroup\$
    – Kirt
    Commented Feb 9 at 23:59
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    \$\begingroup\$ @GMJoe Yes, much like the list of mundane adventuring gear in 5e includes potions of healing. \$\endgroup\$
    – Kirt
    Commented Feb 10 at 0:01
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    \$\begingroup\$ @trlkly I try not too imagine too much what these rules represent, because the D&D combat system is not simulationist and whatever you might imagine will be contradicted at some point. What we think of as armor should make you more likely to get hit, but less likely to take damage. Earlier editions, going back to 1.5, had damage reduction from armor, but 5e doesn't - just a steady progression of getting harder to hit, but no damage reduction. Dexterity helps you avoid being hit - even when you're unconscious. Things like that make me leery of saying that a critical hit is 'in the eyes'. \$\endgroup\$
    – Kirt
    Commented Feb 12 at 7:01

A character absolutely knows they scored a critical hit.[1]

When I was an undergraduate, I fenced competitively (primarily foil, but I sometimes dabbled with epee). In foil, there are a lot of rules which determine whether or not a "hit" actually counts as a touch:

  1. the only valid targets are the torso and groin (the face, arms, and legs are not valid targets),
  2. touches may only be scores if you have "right of way" (essentially, you hit the opponent without having been parried; or you parry your opponent and hit them with the riposte without being parried),
  3. the tip of the weapon must hit hard enough to compress the spring,
  4. and so on...

If you manage to hit your opponent on valid target, with right of way, and so on, you are awarded a "touch" (a point, if you will); a bout goes to 15 touches. Often, you will score valid touches on the very edge of the valid target, or you'll hit after a sloppy parry, or you'll hit your opponent just before they hit you. I once tripped over an untied shoelace, launching myself forward, but managed to keep my balance just long enough to hit someone on their side before falling over. Fencing can get incredibly messy but, as long as you follow the rules, you get the touch. In D&D terms, you beat your opponent's AC and did damage.

Sometimes, however, your technique, strategy, and execution all come together, and you score a really nice touch. Maybe your opponent attempts to parry, but you slip your blade just under theirs and hit them right in the middle of the chest. Or you launch an aggressive fleche and nail your opponent on back with a well-timed flick as you run past them. Perhaps you make a really nice feint, provoke an attack, parry in seven, and nail your opponent in the belly button. At a North American Cup in 2003ish, I fenced a bout against Sean McClain—he was maybe just past his prime, but still one of the best fencers in the world, and I was never going to win that bout. But I did manage to score a single, solitary touch—it was clean, well executed, and felt amazing. These kinds of touches feel good. You know, in your gut, that you dominated your opponent (if only for a moment).

That's the feeling of a critical hit.

[1] There seem to be a couple of questions being asked here. I am going to focus on the question in the title, which is about whether or not a character knows if they have scored a critical hit.

  • \$\begingroup\$ This is a wonderful and interesting description. Thank you for providing it. But I don't think it answers the questions. Feeling good about a hit is good, but it doesn't tell you that damage has been multiplied or that other mechanical aspects have been triggered and certainly doesn't discuss the interplay with adamantine armor. \$\endgroup\$ Commented Feb 13 at 21:02
  • \$\begingroup\$ @TimothyAWiseman What is "damage" and how is it "multiplied"? The rules of D&D are all abstractions, which are meant to very roughly give some sense of what is happening in the game world. When you score a really good touch, you know that you have nailed your opponent. That is the feeling that the notion of a "critical hit" is supposed to convey. With respect to adamantine armor, I very specifically said that I wasn't going to address it (like I said in my footnote, I think that the author of the question is asking several questions). \$\endgroup\$ Commented Feb 13 at 21:23
  • \$\begingroup\$ That is exactly my point. Within the fiction, the concept of a critical hit does not make a lot of sense because it is precisely a hit that does extra damage and triggers certain mechanical effects. It isn't a hit that feels really good, it is a hit that does extra damage. If I get an Ippon that feels great and is recognized by the judge but my opponent gets up without even being winded, I have not gotten a critical hit. If I do a throw that does twice the normal damage I got a critical hit even if it looked horrible, felt bad, and was not recognized as a point. \$\endgroup\$ Commented Feb 14 at 17:41
  • \$\begingroup\$ @TimothyAWiseman A hit which feels really good is a hit that does "extra damage" (again, what is "damage"? that is a game term). A glancing blow is a hit which doesn't feel great---it didn't quite land on target, or it was largely (but not completely) absorbed by the armor. A skilled fencer knows when they have scored a good touch vs when they have scored a barely-passing touch. While fencing is also artificial, you can definitely tell the difference between "I hit the guy, but it was from an odd angle and didn't hurt him too much" vs "I hit that guy hard, right through the heart". \$\endgroup\$ Commented Feb 14 at 18:48
  • \$\begingroup\$ I appreciate your perspective, but I am skeptical that is true, especially when armor is involved. "I hit that guy hard where his heart is, but his armor stopped it" wouldn't even constitute a hit in DnD. "I got a glancing blow, that by pure luck slipped into previously damaged spot and knicked the femoral" is a crit. In judo, a perfect osoto gari probably doesn't hurt uke at all but feels really good for tori. When I lost my own balance and my knee landed in my partner's groin it would have been a crit if my partner hadn't had the right equipment. \$\endgroup\$ Commented Feb 14 at 20:23

Option 1: Game mechanics represent something manifest in the game world

A critical hit, or armor class, hit points, saving throws, ability checks, etc. are the manifestation in our world of something happening in the game world. The characters don’t understand these in the exact same way as the players, but they do understand them.

Option 2: it’s a role playing game

The mechanics are necessary for differentiating an RPG from simple make-believe play. What does a goal represent in football and why should the team that has more of them win after 90 minutes. Who cares! Both are just games and those just happen to be the rules.


does a character know getting stabbed in the eye hurts more than in the foot, I can't think of a reason why not.

Remember game terms may not be meaningful the concepts behind them should be. Do they know a getting stabbed in the eye is a "critical", likely not, but they know it hurts more and adamantine protects against it.

I don't want to rip off a post whole hog, so go read this answer about spell slots and the murky mirror. https://rpg.stackexchange.com/a/131734/37168


Your accepted answer is fine, but let me try a different angle:

The whole fighting system of DnD is perfectly out-of-character. It is a very rough approximation of what actual combat would look like. It abstracts away basically all details and hides them behind probabilities (i.e. D20) and difficulty measurements (i.e., AC) and very crude measures for how good or bad a character is at something (i.e., stat bonuses, proficiency bonuses).

In this regard, DnD 5e is wildly different (simpler) than other systems; for example ones that track damage to individual body parts.

If you think about it, AC is ludicrously crude of a measure, at face value. You are telling me that if someone hits my character there is nothing in the world he can do except hope for the attacker missing?

But all of the previously said is of course a mis-interpretation. AC in truth contains all imaginable ways an attack (and the defense thereof) could play out, from the attacker just being a much better fighter, over me having much better armour, or being faster, or very small or large, or whether a character carries a shield or not, or has scales, and so on. DnD 5e just does not want to spend so much time and complexity in the rules about this and lumps all of it together, and thus opens up plenty of opportunities for role-playing (describing) what happens in-game.

And Critical Hits are just the same: they encapsulate everything that could go so beautifully right for the attacker and could mean that they succeed against otherwise impossible odds. They abstract happy chances away, they hide "pure luck", they contain epic unforeseen story-telling events and so on and forth, all behind a single mechanism.

So yes. In our group, our characters definitely know when they performed a critical hit; the GM will definitely ask us to describe the attack (or does a colorful description themselves) while the player gleefully rolls their bonus damage and enjoys the spotlight.

The characters need no concept of this. They already have the concept that sometimes unexpected great things happen; that the worst person can have the occasional uber-lucky strike, that the awesomest Fighter can occasionally still be hit by a peon due to absolutely bad luck, and so on and forth. They only count on it if they are very foolish (just like the regular buyer of lottery tickets in Real_Life[tm]).

If they have deep insight about that Adamantine Armour, they can very well know (if this is part of what is known in the world at all) that nobody ever, EVER had any luck hitting the wearer of this armour, not even the gods. Or they can learn by experience that over and over again, even if a monster hit them in the most severe fashion whatsoever, the Adamantine still was able to deflect a blow that would have ended any defender wearing a lesser piece. Or they can know some blacksmith who foolishly tried to damage a piece of Adamantine for science, and only managed to break his smithing hammer in two.

As to what keeps your party from bringing that stuff everywhere by default, I guess that's up to the DM, in general - if they want them to not do it, they surely can come up with some direct or indirect cost that makes it unfeasable sometimes.

By request, some sources (in the DnD 5e Player's Handbook):

  • General "spirit" of the game and its understanding of the dice:
    • Pg 5 (introduction): "Anything is possible, but the dice make some outcomes more probable than others."
    • Pg 7 ("The D20"): Gives diverse examples of what a roll of the D20 could mean in-game, similar to the examples I gave above.
  • AC
    • Pg 7: how it works when rolling a hit
    • Pg 14: "Your AC represents how well you character avoids being wounded in battle.", and mentions that many other things than just armur and shield go into this, possibly, for some classes.
    • Pg 144: how armour (the items) and shield work, nothing specifically relevant to this question
    • Pg 177: Mentions that DEX can give a bonus to AC, making clear that AC also encompasses other than just brute force protection, but also includes things like how good the creature is at avoiding hits.
  • Critical Hit
    • 196: a very short, purely technical paragraph detailing what to do with the dice (which are clearly not visible in-game) - the only place in the whole book, at least according to the Index.
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    \$\begingroup\$ AC in truth contains all imaginable ways an attack (and the defense thereof) could play out, from the attacker just being a much better fighter, over me having much better armour, or being faster, or very small or large, or whether a character carries a shield or not, or has scales, and so on. DnD 5e just does not want to spend so much time and complexity in the rules about this and lumps all of it together, and thus opens up plenty of opportunities for role-playing (describing) what happens in-game . Bravo 😎 \$\endgroup\$ Commented Feb 12 at 23:16
  • \$\begingroup\$ I have added some sources, @jack \$\endgroup\$
    – AnoE
    Commented Feb 13 at 12:44

You say:

"I'm trying to figure out if there's any good reason Tier 4 PCs wouldn't bring Adamantine Armor with them when using Astral Projection."

Probably not.

TLDR: Given a chance, those PCs for whom armor is appropriate would likely be fully kitted in it, or maybe carrying a set just in case. They might or might not have every bit of information regarding adamantine armor and its advantages and disadvantages compared to other choices, but they likely have every bit of information that they had the time and resources to gather. So, it's really a question of PC sleuthing, DMing, and world-building.

Tier 4 PCs are likely knowledgeable, powerful, wealthy, and resourceful

Tier 4 PCs (levels 17-20) are described as "masters of the world":

By 17th level, characters have superheroic capabilities, and their deeds and adventures are the stuff of legend. Ordinary people can hardly dream of such heights of power — or such terrible dangers.

In my experience, such characters will do everything in their power to face a significant danger with every tool that can be obtained in the given time and with the given resources.

Tier 4 PCs likely know of adamantine armor

Adamantine armor is merely uncommon. With the defaults presented in the DMG and other source books, Tier 4 PCs, masters of the world, would likely have broad knowledge of uncommon magic items, and so would most likely know of adamantine armor.

Characters with reason to do so, such as those who could wear such armor, given time and reason, would likely know details about it. Its properties. How it compares and contrasts to other expensive armor. Where to obtain.

You need to decide what level of knowledge they have, and is it automatic, a knowledge check, a conversation with an NPC, or a side quest, or potentially, just not available.

Tier 4 PCs likely know of the Astral Plane

Average inhabitants of the default setting might or might not know much about the Astral Plane. Likely their knowledge is rudimentary, apocryphal, fragmentary, and incorrect.

However, Tier 4 PCs are masters of the world, and by definition "traverse otherworldly realms and explore demiplanes and other extraplanar locales". They are likely to have broad knowledge of the planes of existence.

Characters with reason, such as those who could travel to other planes, or who have such connections, or who previously studied such things, would likely know details about the Astral Plane. It's properties. It's inhabitants and dangers.

You need to decide what level of knowledge they have, and is it automatic, a knowledge check, a conversation with an NPC, or a side quest, or potentially, just not available.

Putting it together

So, Tier 4 PCs are quite likely to have general knowledge of adamantine armor and the Astral Plane. How extensive that knowledge is, is up to you. And up to the PCs, for that matter. Given time and resources, they can likely find out most detail available. They are likely to then equip themselves as best as possible.

Your question has the title of "Do characters understand the concept of a 'Critical hit'?"

Yes. They are us, and we are them.

Do they know of natural 20s? Do they conceive of themselves as characters being played by creatures of a higher reality? Whew, you could play it that way. It is a stable of fiction that we mortals are merely pawns of a bigger game played amongst the beings of a higher order of existence.

The rules are quite muddled on the difference between player and character. For instance, the rules routinely change perspective, sometimes talking about players, sometimes talking about characters. From the introduction to the Basic Rules, "How to Play":

Sometimes one player speaks for the whole party, saying, “We’ll take the east door,” for example.

Really . . . it's the character talking about the east door. Or is it?

But the character just needs to know some hits are extraordinary

The player knows a 20 on a die is a critical. The character knows some attacks are better than others.


And any character who's had a chance to prepare, will know that going into the Astral Plane involves significant risk to that precious silver cord, and may will choose to try to mitigate that risk though any way possible, including guarding against the skillful or lucky hits that might sever the silver cord.

I know I would. I mean, my character would.


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