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RAW, total cover differs from half and three-quarters cover insofar as concealment is specified as a prerequisite.

A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

Since the rules never clearly define what constitutes "concealment", a standard meaning, which refers to something being out-of-sight or hidden should be used. But, transparent obstacles do not conceal anything. So, they would only ever grant partial cover, and would practically never grant total cover, according to the RAW. Are there any other defining rules for total cover that would contradict this?

Edit for clarity: it's obvious enough that transparent obstacles can grant some form of cover. My question concerns the RAW, specifically about total cover.

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6 Answers 6

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The cover rules don't address transparent objects, therefore the DM must rule.

Summary: the cover rules don't address cover from transparent objects, the DM must rule; however, in the end, it makes little difference, because transparent objects, depending on the object, provide barriers to attack through other rules, and effectively end up granting total cover.

The cover rules and transparent objects

Transparent objects are not addressed by the cover rules. It isn't a question that transparent objects do or don't grant cover according to the rules, it's that the rules don't say.

The introduction to the cover rules

The introduction to the cover rules says:

Walls, trees, creatures, and other obstacles can provide cover during combat, making a target more difficult to harm.

The examples are opaque, not transparent. However, up to the DM, a transparent object could be an "obstacle"; however, the rules don't say one way or the other.

Certainly in common usage, a glass wall could be an obstacle, but this is an interpretation.

The structure of the cover rules

The paragraphs under Half Cover, Three-Quarters Cover, and Total Cover are all structured the same way. Each one has several sentences, the first sentence provides the result of that type of cover, additional sentences provide a definition, as shown in this table:

Type of Cover First Sentence (result) Additional Sentences (description)
Half Cover A target with half cover has a +2 bonus to AC and Dexterity saving throws. A target has half cover if an obstacle blocks at least half of its body. The obstacle might be a low wall, a large piece of furniture, a narrow tree trunk, or a creature, whether that creature is an enemy or a friend.
Three-Quarters Cover A target with three-quarters cover has a +5 bonus to AC and Dexterity saving throws. A target has three-quarters cover if about three-quarters of it is covered by an obstacle. The obstacle might be a portcullis, an arrow slit, or a thick tree trunk.
Total Cover A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

This is an interpretation.

I believe that the three paragraphs follow a clear result/description pattern, but truthfully, other interpretations are possible. Other answers here argue that the first sentence of the Total Cover paragraph is not a result, but a cause:

A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect.

. . . arguing that this first sentence is not the result, but instead the prerequisite to total cover.

That is also an interpretation. The writing is not clearly unambiguous.

**Finally, the word "concealed"

Finally, under Total Cover, it says,

A target has total cover if it is completely concealed by an obstacle.

"Concealed". Surely a transparent object doesn't "conceal" something. That would be a strange definition of the word concealed.

When the rules aren't clear, the DM interprets

It's easy to look at the rules and make a judgment sans DM. "The rules don't say (or do say) XYZ! Therefore the DM must bend to my will!" That's ridiculous on the face of it. When the rules aren't clear, the DM must interpret.

This itself is obvious in many places, I will just quote one, from the Introduction in the DMG:

As a referee, the DM acts as a mediator between the rules and the players. A player tells the DM what he or she wants to do, and the DM determines whether it is successful or not . . . .

I would further argue that even if the DM wants to be as RAW as possible, the DM must interpret, can't help but interpret, because the rules don't cover every situation, and as is clear here, are sometimes ambiguous or unclear.

How to interpret

My interpretation, the cover rules as not addressing transparent objects, cover is about concealment.

They should have addressed transparent objects, but they didn't. They were (apparently) written on the assumption that visual obscurement and a physical barrier are the same thing, and in many cases, perhaps most, they are, but not in all cases, an extreme example being a solid but transparent barrier.

But furthermore, and most importantly, it doesn't matter.

It doesn't matter because even when fitting the total cover category, sometimes total cover shouldn't prevent an attack, and sometimes something transparent could reasonably block attacks, therefore effectively granting total cover.

We know that physical attacks are blocked by total cover, the rules say so. But, we know the rules don't address every situation, and the DM must rule.

Consider a silk curtain, a paper screen, and an unbreakable magical glass wall. Consider someone with a sword (or a bow). Or really, any other melee weapons. It is entirely reasonable that someone with a sword (or a bow) could, at least under some circumstances, attack through the silk curtain or the paper screen. To rule that the cover rules prohibit these attacks is just ludicrous. I'm sorry, that's pejorative. I believe such a ruling is unfun, breaks the narrative story ludicrously. But other DMs may interpret differently. Now how to interpret such attacks, how does the attacker know where the target is, for instance, that's beyond the scope of this answer.

So, total cover does not grant complete total cover in every conceivable situation. Similarly, a transparent object could block all attacks, effectively granting total cover, even without support from the total cover rules.

Consider the same attacks against an "unbreakable" glass wall. The wall is unbreakable. Obviously the attacks can't get through. We don't need a rule to tell us that, because the opposite (such attacks are allowed because the cover rules don't mention transparent objects) is absurd. Sorry, rather, I think it is obviously absurd, but another DM may wish to rule differently. Now, what happens when the unbreakable glass wall is attacked with the irresistible weapon? Out of scope here, but it has nothing to do with the cover rules.

But what about spells?

Spells require a "clear path". The phrase a "clear path" is regrettably vague. You can argue that a clear path can go through a transparent object.

It is especially vague, because if the "clear path" can't go through something transparent, then it seems there must be some physical component to it, only there doesn't seem to be.

However, to my mind, the most sensible ruling is that "clear path" requires a physical clear path. This is the most sensible ruling, because otherwise casters can cast through all manner of transparent things, such as windows and walls of force, gaining an unreasonably high degree of protection. That seems, at least to me, clearly broken, and therefore magic should not work that way.

However, again, this is DM interpretation. A DM could interpret a "clear path" to allow casting through a window. It would be interesting to hear a report about how that went.

Finally, even if you maintain that a "clear path" is, err, a clear and unambiguous rule, there are edge cases that require DM adjudication. Water, an extremely thin sheet of ice, wet silk, gauze . . . while they may or may not be tough adjudications, the rules certainly don't explicitly say how to handle such cases, so the DM must decide.

What about JC's tweet?

Yes, yes, Jeremy Crawford tweeted:

A solid obstacle, regardless of material, can provide total cover. A closed window counts.

Although unofficial, that is very useful. If only the cover rules actually said that. And also, what does that "can" mean? What do you mean it "can provide total cover". That seems to imply that sometimes a solid obstacle provides total cover and sometimes it doesn't. What?

Conclusion

The cover rules don't address transparent objects one way or another. They just don't. You can squint and maybe they do; but really, they don't. It doesn't matter though, because depending on the narrative, it's obvious that some transparent objects grant the equivalent of total cover to physical attacks, and that the "clear path" required for spell attacks won't go through a solid transparent object.

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  • \$\begingroup\$ this is superb. I tend to think magic that doesn't make attack rolls actually should pass through transparent objects, but this is the answer I was looking for. \$\endgroup\$
    – nonymous
    Commented Jun 24 at 19:27
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    \$\begingroup\$ Well, enemies have more resources than PCs because there are many more of them and they are much more expendable than PCs. So, where a PC has to economize when to use e.g. Misty Step to get past a Wall of Force, an enemy does not. This already makes the efficacy of the Wall somewhat asymmetrical. The "clear path to the target" argument is tautological when Total Cover is in question. \$\endgroup\$
    – nonymous
    Commented Jun 24 at 20:35
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    \$\begingroup\$ We used to play it so that magic used to pass through windows for targeting purposes. It did not really cause any problems and wasn't unbalanced. The number of situations where it matters is generally small, really mostly when you try to cast a spell through a class window, in the early levels and later on, a wall of force. And WoF is so strong, I think it still is a decent spell with that, just not a great one any more. \$\endgroup\$ Commented Jun 25 at 3:54
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    \$\begingroup\$ That said, I think its false to say the rules do not address transprarent obstacles. The rule says the given examples, or "other obstacles" can provide cover - that includes transparent obstacles. As long as those are not exempted explicitly, a general statement like that covers all kinds of obstacles. Else you could claim the game does not cover bronze objects, or white objects, or whatever -- it does not need to, all of them are "other" obstacles, as are transparent ones. \$\endgroup\$ Commented Jun 25 at 3:59
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    \$\begingroup\$ @NobodytheHobgoblin You can certainly read it that way. All the things the cover rules mention, though, are explicitly opaque. Creatures, trees, walls, etc. Finally, under total cover, it says, "A target has total cover if it is completely concealed by an obstacle." "Concealed". Surely a transparent object doesn't "conceal" something. That is a strange definition of the word concealed. My argument is that transparent objects just aren't covered, and the DM needs to interpret. I don't think it's wrong to interpret that transparent objects are covered, it's just that it doesn't say. \$\endgroup\$
    – Jack
    Commented Jun 25 at 9:48
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Yes, there are examples in official sources.

In Tomb of Annihilation, section 69 (Mechanus Chain) we read (emphasis mine):

A rip forms in the vortex high above, and nine cube- shaped creatures with wings and shortbows fly through. They are quickly followed by a large crystal decahedron that holds a weird starfish-shaped creature.

The description of the actions of the creatures involved in this event tells us that (emphasis mine)

The pentadrone can't fly on its own, but it gains a flying speed of 30 feet and can hover while encased in the crystal decahedron, which grants its occupant total cover against attacks that originate outside the vehicle.

So, an object made of crystal, therefore transparent1, can provide total cover.

A classical enemy provides total cover even if it is completely transparent.

The Ooze Cube trait of the Gelatinous Cube tells us that

Ooze Cube. The cube takes up its entire space. Other creatures can enter the space, but a creature that does so is subjected to the cube's Engulf and has disadvantage on the saving throw.

Creatures inside the cube can be seen but have total cover.

There are also examples of the contrary.

There are other cases in which transparent obstacles/defenses do not provide total cover.

The Searing Sunburst of the Way of the Sun Soul subclass says (emphasis mine):

Each creature in that 20-foot-radius sphere must succeed on a Constitution saving throw or take 2d6 radiant damage. A creature doesn’t need to make the save if the creature is behind total cover that is opaque.

A Wall of Force may provide total cover against physical attacks, but not from this particular feature.


The last example clarifies that total cover mechanics depends on both the game feature (item, spell, class feature) that is providing it and on the game feature one is protecting from (attack, spell's AoE, class feature).


1 From the Cambridge dictionary: clear, transparent rock that is used in jewellery, or a piece of this; transparent rock that looks like ice, or a piece of it; transparent glass of high quality, usually with its surface cut into patterns that reflect light; A crystal is a transparent glass or plastic cover for a watch or clock.

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    \$\begingroup\$ @nonymous In these cases, one uses the common English meaning: from Cambridge dictionary "transparent glass of very high quality, usually with its surface cut into delicate patterns". \$\endgroup\$
    – Eddymage
    Commented Jun 24 at 18:13
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    \$\begingroup\$ Sure. But, it's still a matter of specific beating general. The Gelatinous Cube example is interesting, but the wording "Creatures inside the cube can be seen but have total cover." seems to suggest this is an exception to the general rule. \$\endgroup\$
    – nonymous
    Commented Jun 24 at 18:17
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    \$\begingroup\$ @nonymous Again, your comments suggest that you have made up your mind even before posting the question: as already suggested by others, I invite you to write your own answer. \$\endgroup\$
    – Eddymage
    Commented Jun 24 at 18:25
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    \$\begingroup\$ Thank you for taking the time to find examples that specifically address whether the rules on cover and concealment are definitional or an example. I think these address nonymous' objection pretty squarely. I wanted to look for some, started with Tomb of Levistus, got discouraged, and quit. W/rt searing sunburst, it seems to be an exception specifically because the attack itself is LIGHT, which passes through anything transparent and does not treat a barrier as cover unless it is opaque. \$\endgroup\$
    – Kirt
    Commented Jun 24 at 18:50
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    \$\begingroup\$ I agree that assuming that "crystal" is transparent is not warranted. While, sure there is a meaning of crystal that means "ultra clear glass," there is also the more common meaning that refers things like gemstones, which are not generally transparent. This is especially so since it mentions a decahedron, which is a common crystal formation for gems, but not for glass. \$\endgroup\$
    – trlkly
    Commented Jun 25 at 6:24
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Yes they do; concealment is not a prerequisite

The cover rules open with:

Walls, trees, creatures, and other obstacles can provide cover during combat, making a target more difficult to harm.

What matters for cover is whether the thing that is interposing between you and the target is an obstacle. This is a general rule. It applies to all kinds of obstacles, transparent, intransparent, you name it. (And it does not need to call out transparent objects, just as it does not need to call out blue or wooden objects, because these are covered by a general statement by default, too).

Total cover is just a type of cover and is defined like this:

A target with total cover can’t be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect.

So if due to an obstacle there is no direct or unbroken line of effect or "path to the target" from the source of the effect to your target, the target has total cover.

The sentence about concealment then gives just one example case where a target has total cover. It is not defining what total cover is. For concealment to be a prerequisite, the sentence would need to say “A target has total cover only if it is completely concealed by an obstacle.", but it does not say that. Nothing in the rules says transparent obstacles do not provide cover.

Your question is based on a logical fallacy: the fact that an obstacle which completely conceals provides total cover, does not mean that an obstacle that does not completely conceal cannot provide total cover. That you can drink a green liquid does not mean all liquids must be green for you to be able to drink them. Concealment is a sufficient condition for total cover, not a necessary one. This is not a flaw in the rules; it is an error in reading them. If there's any flaw here, then maybe it is that it is possible to misread them this way.

If an opaque obstacle conceals a target completely, it must have total cover from you. The obstacle is so large that it blocks all lines of effect, and because it is opaque, it also conceals the target. You can use that as a check to see whether the target has total cover. But what matters is that the obstacle blocks all lines of effect, not whether the target is visible.

You can also see this from the rules for resolving cover on a grid (DMG, p. 251)

To determine whether a target has cover against an attack or other effect on a grid, choose a corner of the attacker's space or the point of origin of an area of effect. Then trace imaginary lines from that corner to every corner of any one square the target occupies. If one or two of those lines are blocked by an obstacle (including another creature), the target has half cover. If three or four of those lines are blocked but the attack can still reach the target (such as when the target is behind an arrow slit), the target has three-quarters cover.

What matters is whether you can draw a line to the target that is not blocked by an obstacle, not whether you can see the target or not.

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What is "total cover"?

The rules introduce "total cover" in the context of two things — attacks and spellcasting:

A target with total cover can't be targeted directly by an attack or a spell

We already know you can't cast spells through things, unless the spell explicitly says otherwise.

So the question is — can you hit something you have no physical access to, although you can see (a part of) it? Common sense says you can't. Therefore, a transparent obstacle grants all the benefits of total cover.

But the rules say the target has to be "concealed"...

I believe this takes RAW beyond realms of extreme rules lawyering. If we ignore common sense and only stick to the RAW, it leads to unpredictable and ridiculous issues. In some cases, RAW fall short. The writers, after all, are only human and can miss details.

Here's an armored door with transparent parts. You can definitely see through it: a free image from iStock

Good luck to DM, describing a PC attacking through a closed door, since "it only grants partial cover by RAW".

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    \$\begingroup\$ You can't cast spells through things because of the cover rules. "can you hit something you have no physical access to, although you can see (a part of) it?" Common sense says you can shove a sword through a thin enough pane of glass at someone on the other side. \$\endgroup\$
    – Caleth
    Commented Jun 24 at 14:22
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    \$\begingroup\$ @Caleth destructible obstacles is completely another question, this it not what OP asks. \$\endgroup\$
    – enkryptor
    Commented Jun 24 at 14:30
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    \$\begingroup\$ "You can't cast spells through things because of the cover rules" — negative. You can't cast through things because casting a spell needs "a clear path to the target". \$\endgroup\$
    – enkryptor
    Commented Jun 24 at 14:32
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    \$\begingroup\$ I'm suggesting that something might not be an obstacle if it is transparent, and therefore you can't have total cover behind it \$\endgroup\$
    – Caleth
    Commented Jun 24 at 14:42
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    \$\begingroup\$ "Clear" can have equivocal meanings, especially in with reference to transparency and concealment. There is no obvious rationale why a spell that makes no attack roll , like Mind Sliver, should require a clear physical path. \$\endgroup\$
    – nonymous
    Commented Jun 24 at 15:14
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What is an obstacle?

It seems to me that the word "concealed" is ambiguous here, and the other answers discuss that aspect of the question quite in depth. So instead, I'll focus on the other problematic point of the question : what is defined as an "obstacle" here?

The reason for asking this is the following : whether or not sight is needed, you'd need the glass object to be considered as an "obstacle" for it to grant cover.

The word "obstacle", from the latin "obstare" which roughly translates to "impede", is defined online as follows :

A thing that blocks one's way or prevents or hinders progress.

As such, an object can be defined as an obstacle to something if it makes it more difficult for something to pass through, or straight up prevents it completely.

There are a few possible ways to interpret this definition, and each of them has different consequences on the game.

Reading 1 : if it blocks anything, it grants cover

The simplest reading is the following : if the object could block anything that's concerned by the cover rules, then it counts as cover.

While glass does not block light (or sight, if you prefer), it will block other things such as movement. Using this reading, a transparent object would effectively grant cover.

Reading 2 : if it can block it, it grants cover specifically for it

This is a more "realistic" approach, but which also adds more complexity. Something that might be an obstacle in a situation may not even be a bother in another. The simplest example is, once again, sight versus movement, but there are other examples which may make more sense.

For instance, while a thin pane of glass is going to prevent gas or liquids from going through, is it really going to protect you against a mace or a crossbow shot?

In such a situation, it would be more "realistic" to decide that the glass object counts as cover for certain actions or features, but does not for other.

In the case of this reading, what counts as cover or not would have to be defined by the DM, although they could also definitely keep this reading as an edge-case type of thing, and use the first reading for most situations.

So, can a transparent object grant cover?

With the first reading, yes, any transparent object that presents at least some kind of physical blocking ability would count as cover no matter what.

With the second reading, it would be more of a case-by-case situation, where the DM decides whether or not cover is granted for each feature, and where the object could simultaneously count as cover for something, and not count as cover for something else.

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  • \$\begingroup\$ "So, can a transparent object grant cover?" Obviously. The question is about total cover \$\endgroup\$
    – nonymous
    Commented Jun 24 at 15:22
  • \$\begingroup\$ @nonymous it's not obvious if a transparent object is or is not an obstacle. If it isn't, it doesn't matter whether or not it conceals \$\endgroup\$
    – Caleth
    Commented Jun 24 at 15:33
  • \$\begingroup\$ @Caleth, while there are instances of transparent object that can/cannot qualify as obstacles, I take it for granted that some transparent objects can be obstacles. Hence, my claim that obviously [some] transparent objects can grant cover. But, I was taking exception with Matthieu's phrasing, because my concern here is specifically about total cover and not cover in general. \$\endgroup\$
    – nonymous
    Commented Jun 24 at 16:54
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For RAW, it doesn't.

It would appear that glass fails as having the prerequisites of being something for total cover. In addition, most uses of the word "concealed" are used in a similar manner, with no indication of it being different than the normal use functions of the word.

For RAI: It provides total cover.

Jeremy Crawford in a tweet clarifies this. However, since this is Jeremy Crawford and not an official source, you should still ask your DM.

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