TBH i find D&D 5E always struggled with the concept of Darkness & Vision, even 4E did IIRC, mainly because they always insisted in handling mundane and magical darkness the same way with heavily obscured.
Darkness that can be illuminated by light shouldn't be opaque to it so i make an exception for logic reasons.
That's fine if you want to interpret it that way. But you better be consistent.
If your party is standing outside at night, surrounded by an area of Darkness (as the books declare) then your party cannot see the crescent moon and the stars. They cannot see the light from the bustling tavern on the hill. They cannot see each other's torches if they stand more than a few feet away.
All is inky opaque darkness.
All is heavy obscurement.
All hope is lost...
I mean... yeah. I rule that any area that has any kind of illumination is in Dim Light, not Darkness. If the moon illuminates the night, or if you are near a bustling tavern, you are not in Darkness, you are in Dim Light. I reserve Darkness for caves, or closed rooms with no windows or source of light. If I say an area is in Darkness, it's pitch-black Darkness. Is it consistent with real world physics? No, but most of the mechanical rules of this game aren't...
Realistically, if you stand in Darkness and you look at a target standing in the light, you can see them, but they can't see you. But the game simply isn't designed to handle such a case.
That's fine if you want to interpret it that way. But you better be consistent.
If your party is standing outside at night, surrounded by an area of Darkness (as the books declare) then your party cannot see the crescent moon and the stars. They cannot see the light from the bustling tavern on the hill. They cannot see each other's torches if they stand more than a few feet away.
All is inky opaque darkness.
All is heavy obscurement.
All hope is lost...
I mean... yeah. I rule that any area that has any kind of illumination is in Dim Light, not Darkness. If the moon illuminates the night, or if you are near a bustling tavern, you are not in Darkness, you are in Dim Light. I reserve Darkness for caves, or closed rooms with no windows or source of light. If I say an area is in Darkness, it's pitch-black Darkness. Is it consistent with real world physics? No, but most of the mechanical rules of this game aren't...
Realistically, if you stand in Darkness and you look at a target standing in the light, you can see them, but they can't see you. But the game simply isn't designed to handle such a case.
Then you disobey those rules which are, by definition, correct.
The PHB says quite clearly: "Characters face Darkness outdoors at night (even most moonlit nights)". Darkness. Heavily Obscured. Opaque.
Realistically, darkness isn't opaque because darkness has no surface or volume.
Nothing in the rules of the game imply that magical darkness behaves differently in general to natural darkness, beyond any differences described in each magical effect. If your magical darkness is an opaque inky volume, then so should your natural darkness, and therefore the night is completely dark with no visible anything.
It's still better than making up an entirely new set of rules like you do, which unnecessarily complicate the game just to add more realism. This game is not meant to be realistic. It's meant to be simple to grasp. If you want to overcomplicate things for the sake of realism, you can play AD&D 2e, I guess.
It's still better than making up an entirely new set of rules...
Strictly mechanically speaking, all the rules for Heavily Obscured (including Darkness) say is that you have the Blinded condition when trying to see something inside. They don't say anything, either way, about seeing out of or through darkness. It's left to the judgment of the DM (there are hints, and people like to read those hints in either direction).
You don't need an entirely new set of rules to decide that you can see the moon or stars on a full-dark night, or that you can see torches in the distance, or... Same for A being able to see D or (C or E) being able to see (A or D) in that diagram. It's the DM's call, and probably the only important thing is to be consistent at the table (and consistency between tables doesn't matter to any individual game). It's eminently fine to to be able to see out of / through Darkness and not out of / through heavy fog, and not even that complicated.
It's still better than making up an entirely new set of rules...
Strictly mechanically speaking, all the rules for Heavily Obscured (including Darkness) say is that you have the Blinded condition when trying to see something inside. They don't say anything, either way, about seeing out of or through darkness. It's left to the judgment of the DM (there are hints, and people like to read those hints in either direction).
You don't need an entirely new set of rules to decide that you can see the moon or stars on a full-dark night, or that you can see torches in the distance, or... Same for A being able to see D or (C or E) being able to see (A or D) in that diagram. It's the DM's call, and probably the only important thing is to be consistent at the table (and consistency between tables doesn't matter to any individual game). It's eminently fine to to be able to see out of / through Darkness and not out of / through heavy fog, and not even that complicated.
I know you're generally agreeing with me, but I wouldn't let the rule books off so lightly. There is a fundamental conflict in the way they have drafted this set of rules.
1. Heavily Obscured areas give the blinded condition when looking into.
2. Heavily Obscured areas are opaque.
3. An area of darkness is a Heavily Obscured area.
4. Outside at night is darkness.
All agree on point one and its mechanical effect.
The conflict is in 2-4.
An illustration: how do we know that you cannot see through to the other side of the Fog Cloud spell? The spell description doesn't say that, it just says the area is Heavily Obscured. We look up that rule and know that a Heavily Obscured area is opaque and thus the fog effect is fully defined.
What about the Darkness spell? The description says it creates an area of darkness. The rule for darkness links to the rules for a Heavily Obscured area - so people would not be wrong for assuming the area is opaque.
A problem: the rules for non-magical darkness lead to the same place, and natural darkness is not restricted to only the darkest of pitch black caves - it is standard night time.
So people come up with an assortment of "solutions":
A. Magical darkness and natural darkness are just different somehow.
B. Night isn't Darkness.
C. Darkness isn't an area.
D. Heavily Obscured areas aren't all opaque.
None agree fully with the rules as written. There is no RAW that works.
It is important to pick an interpretation, communicate with players as early as it might be important, and be considerate of others who might have read these same rules, come to another perfectly logical conclusion and then made assumptions about how their character was going to work under that logic.
2. Heavily Obscured areas are opaque. ... 4. Outside at night is darkness. ... The conflict is in 2-4.
Yes, that is exacly where the conflict lies, and is the only source of the conflict. That one word, "opaque," which isn't a strict mechanical term, nor is anything keyed off it. It's just language. (I mean, all rules are just language, which is why RAW is always interpretive, but usually writers go out of their way when they want things to mean special things.)
An illustration: how do we know that you cannot see through to the other side of the Fog Cloud spell? The spell description doesn't say that, it just says the area is Heavily Obscured. We look up that rule and know that a Heavily Obscured area is opaque and thus the fog effect is fully defined. What about the Darkness spell? The description says it creates an area of darkness. The rule for darkness links to the rules for a Heavily Obscured area - so people would not be wrong for assuming the area is opaque.
People (usually) have lived experience of being in fog, or looking through fog, and being in darkness, looking across darkness, etc. You can't see the other side of the fog; you can see the other side of the darkness. This isn't RAW being "broken" (clearly it's usable); it's RAW being messy and unclear (hah).
There are two types of Magical Darkness, there the normal Darkness and their is the Darkness Spell. They both are the same, except Darkvision doesn't work in the spell.
Otherwise you can't see in or out of the Darkness, which is typically a sphere, without some magical/enchanced senses.
Night darkness or a dark dungeon or room is treated the same, except you can simply light something to see a certain distance around you and of course Darkvision works, but doesn't see anything in color.
People (usually) have lived experience of being in fog, or looking through fog, and being in darkness, looking across darkness, etc. You can't see the other side of the fog; you can see the other side of the darkness. This isn't RAW being "broken" (clearly it's usable); it's RAW being messy and unclear (hah).
No, its RAW being broken. The fundamental problem is that whether an area blocks line of sight matters, and thus darkness and fog should not be the same effect.
3.5e and 4e both understood this, and when an effect was supposed to block vision through it said so specifically. For example, 3.5e fog cloud:
The fog obscures all sight, including darkvision, beyond 5 feet. A creature within 5 feet has concealment (attacks have a 20% miss chance). Creatures farther away have total concealment (50% miss chance, and the attacker can’t use sight to locate the target).
or the 4e wall of fog:
The wall is heavily obscured and blocks line of sight.
3.5e dealt with the balance problem of non-opaque darkness by just changing the effect to dimness
This spell causes an object to radiate shadowy illumination out to a 20-foot radius. All creatures in the area gain concealment (20% miss chance).
So, this isn't some new problem that was never noticed before; it's a problem 5e created. They had access to prior editions, they just refused to learn from them.
... People (usually) have lived experience of being in fog, or looking through fog, and being in darkness, looking across darkness, etc. You can't see the other side of the fog; you can see the other side of the darkness. This isn't RAW being "broken" (clearly it's usable); it's RAW being messy and unclear (hah).
So messy and unclear that in the last ten posts 4 people have argued for 4 different logically sound positions.
MPA argues A - natural/magical darkness is different.
Natrel argues B - night isn't darkness.
I argue C - darkness doesn't function as an area/volume.
You argue D - Heavily Obscured areas are not always opaque.
There have been no dramatic logical fallacies involved, we just all read and interpret the same text in different ways which have genuinely important mechanical implications.
There have been no dramatic logical fallacies involved, we just all read and interpret the same text in different ways which have genuinely important mechanical implications.
And every one of them is able to play the game without it falling apart. That's what I mean by "not broken." Their DM decides, one way or the other. Consensus doesn't matter (especially on the internet).
If so, I answered to the image made by Wysperra with the next comment:
(again, no special senses involved)
- No Cover in any case. - A can see and target B no problem. And vice-versa. - A has the Blinded condition while trying to see or target C, D and E. And vice-versa. Spells or game features that say "that you can see" are affected. - C has the Blinded condition when trying to see or target E. And vice-versa. Spells or game features that say "that you can see" are affected.
For Tarod: I'm curious - Why does A have the blinded condition when trying to see D? D is not in an area that is heavily obscured.
Heavily Obscured
You have the Blinded condition while trying to see something in a Heavily Obscured space. D is not in a heavily obscured space. I can understand saying that A simply cannot see D (I know there's contention about that as well), but I'm confused why they would have the Blinded condition. What is giving them that condition? Do you automatically have the Blinded condition when you cannot see something?
Sorry, this isn't an argument for any interpretation. I've genuinely curious. Nothing in the rules states that an area that is Heavily Obscured would create Cover (Cover is defined as being created by an "Object", although it allows for Creatures to generate Cover as well), so I don't know that we can say the Darkness would create Total Cover for D vs A. I'm just not quite sure what rules intersect to determine what happens between A trying to target D.
For the OP, here's how I personally rule it, based on the image above (and assuming no creature has Darkvision):
A and B can target each other no problem. A has the Blinded condition when targeting C & E. C & E can target A normally. C is blinded when trying to target E (and vice versa). A can target D normally.
Here's my explanation:
Magical Darkness is the same as mundane Darkness except for anything specific in the spell that changes it (such as the Darkness spell affecting Darkvision). We know characters can see through Darkness to lit areas (both dimly lit and brightly lit) because characters can see a campfire from 100 feet away, even when they themselves are in an area of Darkness (mundane). They can see the moon and stars. Etc.
So I like to simplify the scenario to make it less "weird and magical". There isn't any real difference between C being in magical Darkness and A being in normal daylight VERSUS C being in mundane Darkness (nighttime) and A standing next to a roaring campfire. If A is by the campfire, they are in a brightly lit area, in which case they can be targeted normally. We'll say a campfire gives off the same amount of light as a torch (20 feet bright light, then 20 feet dim light). If C is 50 feet away, they are in Darkness. But we wouldn't say that they cannot see the campfire/torch, right? A would be able to be targeted by spells that say "a target you can see" normally, because they aren't behind Cover and they are in a Brightly Lit area. This is the same as the scenario in the picture above, except the frame of reference is shifted. The reality is the same: A is in a Brightly Lit area, and C is in Darkness.
As for A and D, that's the weirdest and most confusing. But we could think of it the same way as our example with the campfire/torch. A is in an area of bright light, and D is in an area of bright light. Say they are both by a torch but are 60 feet away from each other. Their torch's areas of light don't overlap, so there is darkness between them. But would we say they can then not target each other? That would seem silly.
Now people can argue about "if you can see the torch, then you would see the silhouette of something in the darkness and therefore should be able to target them" and yes, I get that (I think depth perception and whatnot would come in to play, so it wouldn't be easy to target them anyway, but...), however D&D is not a physics simulator, so we can't try to apply real world physics to every situation.
For Tarod: I'm curious - Why does A have the blinded condition when trying to see D? D is not in an area that is heavily obscured.
He's treating magical darkness as opaque, so it blocks line of sight through. Opaque heavy concealment is
A can see and be seen by B
B can see and be seen by A and D
C cannot see or be seen by anyone.
D can see and be seen by B
E cannot see or be seen by anyone.
Non-opaque heavy concealment is
Everyone can see A, B, and D.
No-one can see C or E.
The problem with treating darkness as non-opaque heavy concealment is that doing so is hilariously overpowered.
Sure, but does blocking line of sight grant the Blinded Condition specifically?
Do you have the Blinded condition to anything you can't see? And if so, why wouldn't the Invisible condition simply say creatures have the Blinded condition when attempting to see you?
Sure, but does blocking line of sight grant the Blinded Condition specifically?
For some reason, that's how 5.5e likes to implement being unable to see. Honestly, a coherent writeup of vision rules wouldn't use blinded that way at all, it would be
Blinded: a blind character cannot see unless they have a special ability that allows them to do so. See Unseen Attackers and Targets.
Darkness: creatures in darkness cannot be seen unless the observer has a special ability that allows them to do so. See Unseen Attackers and Targets.
Heavily Obscured: a heavily obscured area blocks line of sight; creatures cannot into, out of, or through the area unless they have a special ability that allows them to do so. See Unseen Attackers and Targets.
Invisible: an invisible creature cannot be seen, unless the observer has a special ability that allows them to do so. See Unseen Attackers and Targets.
Unseen Attackers and Targets: promote this into the glossary.
This wording lets any sources of magical darkness specify whether they're opaque -- if it says "heavily obscured" they're opaque, otherwise it's just darkness.
Sure, but does blocking line of sight grant the Blinded Condition specifically?
For some reason, that's how 5.5e likes to implement being unable to see. Honestly, a coherent writeup of vision rules wouldn't use blinded that way at all, it would be
Blinded: a blind character cannot see unless they have a special ability that allows them to do so. See Unseen Attackers and Targets.
Darkness: creatures in darkness cannot be seen unless the observer has a special ability that allows them to do so. See Unseen Attackers and Targets.
Heavily Obscured: a heavily obscured area blocks line of sight; creatures cannot into, out of, or through the area unless they have a special ability that allows them to do so. See Unseen Attackers and Targets.
Invisible: an invisible creature cannot be seen, unless the observer has a special ability that allows them to do so. See Unseen Attackers and Targets.
Unseen Attackers and Targets: promote this into the glossary.
This wording lets any sources of magical darkness specify whether they're opaque -- if it says "heavily obscured" they're opaque, otherwise it's just darkness.
I think that would be better. Currently there if you cannot see something it might be because they have the Invisible condition, they are behind Total Cover, you have the Blinded condition, or they are just "unseen" as described in the Unseen Attackers and Targets section. They each have different rules, but some of them seem to overlap a lot (i.e. having the Invisible condition does some things that the Blinded condition does, but also impacts initiative. Same with the Unseen Attackers and Targets portion.
It makes me wonder why they got rid of the Line of Sight description from 5e for 5.5e.
Line of Sight: To precisely determine whether there is line of sight between two spaces, pick a corner of one space and trace an imaginary line from that corner to any part of another space. If at least one such line doesn't pass through or touch an object or effect that blocks vision - such as a stone wall, a thick curtain, or a dense cloud of fog- then there is line of sight.
Then in each spell it could simply state whether it blocks vision (I believe there are specific examples of this already with certain "Wall of...." spells). Fog cloud? Blocks vision. Darkness? Doesn't block vision (or does).
As such, the relationship between A and D in the picture is pretty well undefined by RAW in 5.5e. We can certainly make determinations, but it doesn't seem as though there's a real RAW answer for it.
Oh, that's my bad. I don't have the updated ruleset; I don't have access to the new DMG. I go based on the 5.5e Basic Rules, which doesn't include the Line of Sight rules (as far as I've found).
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TBH i find D&D 5E always struggled with the concept of Darkness & Vision, even 4E did IIRC, mainly because they always insisted in handling mundane and magical darkness the same way with heavily obscured.
Darkness that can be illuminated by light shouldn't be opaque to it so i make an exception for logic reasons.
I mean... yeah. I rule that any area that has any kind of illumination is in Dim Light, not Darkness. If the moon illuminates the night, or if you are near a bustling tavern, you are not in Darkness, you are in Dim Light.
I reserve Darkness for caves, or closed rooms with no windows or source of light. If I say an area is in Darkness, it's pitch-black Darkness.
Is it consistent with real world physics? No, but most of the mechanical rules of this game aren't...
Realistically, if you stand in Darkness and you look at a target standing in the light, you can see them, but they can't see you.
But the game simply isn't designed to handle such a case.
Then you disobey those rules which are, by definition, correct.
The PHB says quite clearly: "Characters face Darkness outdoors at night (even most moonlit nights)". Darkness. Heavily Obscured. Opaque.
Realistically, darkness isn't opaque because darkness has no surface or volume.
Nothing in the rules of the game imply that magical darkness behaves differently in general to natural darkness, beyond any differences described in each magical effect. If your magical darkness is an opaque inky volume, then so should your natural darkness, and therefore the night is completely dark with no visible anything.
It's still better than making up an entirely new set of rules like you do, which unnecessarily complicate the game just to add more realism. This game is not meant to be realistic. It's meant to be simple to grasp. If you want to overcomplicate things for the sake of realism, you can play AD&D 2e, I guess.
Strictly mechanically speaking, all the rules for Heavily Obscured (including Darkness) say is that you have the Blinded condition when trying to see something inside. They don't say anything, either way, about seeing out of or through darkness. It's left to the judgment of the DM (there are hints, and people like to read those hints in either direction).
You don't need an entirely new set of rules to decide that you can see the moon or stars on a full-dark night, or that you can see torches in the distance, or... Same for A being able to see D or (C or E) being able to see (A or D) in that diagram. It's the DM's call, and probably the only important thing is to be consistent at the table (and consistency between tables doesn't matter to any individual game). It's eminently fine to to be able to see out of / through Darkness and not out of / through heavy fog, and not even that complicated.
I know you're generally agreeing with me, but I wouldn't let the rule books off so lightly. There is a fundamental conflict in the way they have drafted this set of rules.
1. Heavily Obscured areas give the blinded condition when looking into.
2. Heavily Obscured areas are opaque.
3. An area of darkness is a Heavily Obscured area.
4. Outside at night is darkness.
All agree on point one and its mechanical effect.
The conflict is in 2-4.
An illustration: how do we know that you cannot see through to the other side of the Fog Cloud spell? The spell description doesn't say that, it just says the area is Heavily Obscured. We look up that rule and know that a Heavily Obscured area is opaque and thus the fog effect is fully defined.
What about the Darkness spell? The description says it creates an area of darkness. The rule for darkness links to the rules for a Heavily Obscured area - so people would not be wrong for assuming the area is opaque.
A problem: the rules for non-magical darkness lead to the same place, and natural darkness is not restricted to only the darkest of pitch black caves - it is standard night time.
So people come up with an assortment of "solutions":
A. Magical darkness and natural darkness are just different somehow.
B. Night isn't Darkness.
C. Darkness isn't an area.
D. Heavily Obscured areas aren't all opaque.
None agree fully with the rules as written. There is no RAW that works.
It is important to pick an interpretation, communicate with players as early as it might be important, and be considerate of others who might have read these same rules, come to another perfectly logical conclusion and then made assumptions about how their character was going to work under that logic.
Yes, that is exacly where the conflict lies, and is the only source of the conflict. That one word, "opaque," which isn't a strict mechanical term, nor is anything keyed off it. It's just language. (I mean, all rules are just language, which is why RAW is always interpretive, but usually writers go out of their way when they want things to mean special things.)
People (usually) have lived experience of being in fog, or looking through fog, and being in darkness, looking across darkness, etc. You can't see the other side of the fog; you can see the other side of the darkness. This isn't RAW being "broken" (clearly it's usable); it's RAW being messy and unclear (hah).
There are two types of Magical Darkness, there the normal Darkness and their is the Darkness Spell. They both are the same, except Darkvision doesn't work in the spell.
Otherwise you can't see in or out of the Darkness, which is typically a sphere, without some magical/enchanced senses.
Night darkness or a dark dungeon or room is treated the same, except you can simply light something to see a certain distance around you and of course Darkvision works, but doesn't see anything in color.
No, its RAW being broken. The fundamental problem is that whether an area blocks line of sight matters, and thus darkness and fog should not be the same effect.
3.5e and 4e both understood this, and when an effect was supposed to block vision through it said so specifically. For example, 3.5e fog cloud:
or the 4e wall of fog:
3.5e dealt with the balance problem of non-opaque darkness by just changing the effect to dimness
So, this isn't some new problem that was never noticed before; it's a problem 5e created. They had access to prior editions, they just refused to learn from them.
So messy and unclear that in the last ten posts 4 people have argued for 4 different logically sound positions.
MPA argues A - natural/magical darkness is different.
Natrel argues B - night isn't darkness.
I argue C - darkness doesn't function as an area/volume.
You argue D - Heavily Obscured areas are not always opaque.
There have been no dramatic logical fallacies involved, we just all read and interpret the same text in different ways which have genuinely important mechanical implications.
And every one of them is able to play the game without it falling apart. That's what I mean by "not broken." Their DM decides, one way or the other. Consensus doesn't matter (especially on the internet).
If the rules are unusable as written and everyone house rules them to make sense, the rules are broken.
For Tarod: I'm curious - Why does A have the blinded condition when trying to see D? D is not in an area that is heavily obscured.
Heavily Obscured
You have the Blinded condition while trying to see something in a Heavily Obscured space. D is not in a heavily obscured space. I can understand saying that A simply cannot see D (I know there's contention about that as well), but I'm confused why they would have the Blinded condition. What is giving them that condition? Do you automatically have the Blinded condition when you cannot see something?
Sorry, this isn't an argument for any interpretation. I've genuinely curious. Nothing in the rules states that an area that is Heavily Obscured would create Cover (Cover is defined as being created by an "Object", although it allows for Creatures to generate Cover as well), so I don't know that we can say the Darkness would create Total Cover for D vs A. I'm just not quite sure what rules intersect to determine what happens between A trying to target D.
For the OP, here's how I personally rule it, based on the image above (and assuming no creature has Darkvision):
A and B can target each other no problem.
A has the Blinded condition when targeting C & E.
C & E can target A normally.
C is blinded when trying to target E (and vice versa).
A can target D normally.
Here's my explanation:
Magical Darkness is the same as mundane Darkness except for anything specific in the spell that changes it (such as the Darkness spell affecting Darkvision). We know characters can see through Darkness to lit areas (both dimly lit and brightly lit) because characters can see a campfire from 100 feet away, even when they themselves are in an area of Darkness (mundane). They can see the moon and stars. Etc.
So I like to simplify the scenario to make it less "weird and magical". There isn't any real difference between C being in magical Darkness and A being in normal daylight VERSUS C being in mundane Darkness (nighttime) and A standing next to a roaring campfire. If A is by the campfire, they are in a brightly lit area, in which case they can be targeted normally. We'll say a campfire gives off the same amount of light as a torch (20 feet bright light, then 20 feet dim light). If C is 50 feet away, they are in Darkness. But we wouldn't say that they cannot see the campfire/torch, right? A would be able to be targeted by spells that say "a target you can see" normally, because they aren't behind Cover and they are in a Brightly Lit area. This is the same as the scenario in the picture above, except the frame of reference is shifted. The reality is the same: A is in a Brightly Lit area, and C is in Darkness.
As for A and D, that's the weirdest and most confusing. But we could think of it the same way as our example with the campfire/torch. A is in an area of bright light, and D is in an area of bright light. Say they are both by a torch but are 60 feet away from each other. Their torch's areas of light don't overlap, so there is darkness between them. But would we say they can then not target each other? That would seem silly.
Now people can argue about "if you can see the torch, then you would see the silhouette of something in the darkness and therefore should be able to target them" and yes, I get that (I think depth perception and whatnot would come in to play, so it wouldn't be easy to target them anyway, but...), however D&D is not a physics simulator, so we can't try to apply real world physics to every situation.
He's treating magical darkness as opaque, so it blocks line of sight through. Opaque heavy concealment is
Non-opaque heavy concealment is
The problem with treating darkness as non-opaque heavy concealment is that doing so is hilariously overpowered.
Sure, but does blocking line of sight grant the Blinded Condition specifically?
Do you have the Blinded condition to anything you can't see? And if so, why wouldn't the Invisible condition simply say creatures have the Blinded condition when attempting to see you?
For some reason, that's how 5.5e likes to implement being unable to see. Honestly, a coherent writeup of vision rules wouldn't use blinded that way at all, it would be
This wording lets any sources of magical darkness specify whether they're opaque -- if it says "heavily obscured" they're opaque, otherwise it's just darkness.
I use rules for Unseen Attackers and Targets
I think that would be better. Currently there if you cannot see something it might be because they have the Invisible condition, they are behind Total Cover, you have the Blinded condition, or they are just "unseen" as described in the Unseen Attackers and Targets section. They each have different rules, but some of them seem to overlap a lot (i.e. having the Invisible condition does some things that the Blinded condition does, but also impacts initiative. Same with the Unseen Attackers and Targets portion.
It makes me wonder why they got rid of the Line of Sight description from 5e for 5.5e.
Line of Sight: To precisely determine whether there is line of sight between two spaces, pick a corner of one space and trace an imaginary line from that corner to any part of another space. If at least one such line doesn't pass through or touch an object or effect that blocks vision - such as a stone wall, a thick curtain, or a dense cloud of fog- then there is line of sight.
Then in each spell it could simply state whether it blocks vision (I believe there are specific examples of this already with certain "Wall of...." spells). Fog cloud? Blocks vision. Darkness? Doesn't block vision (or does).
As such, the relationship between A and D in the picture is pretty well undefined by RAW in 5.5e. We can certainly make determinations, but it doesn't seem as though there's a real RAW answer for it.
They didn't, it's pretty much unchanged. https://www.dndbeyond.com/sources/dnd/dmg-2024/running-the-game#LineofSight. Problem is, no effects in the game state whether they block line of sight (a few state they are opaque, mostly wall spells).
Oh, that's my bad. I don't have the updated ruleset; I don't have access to the new DMG. I go based on the 5.5e Basic Rules, which doesn't include the Line of Sight rules (as far as I've found).