As long as the rules do not say how Darkvision works, it is entirely up to the DM to decide whether reflections are visible for a creature with Darkvision. Personally, I would rule that reflections can be seen by a creature with Darkvision.
However, the statement that nothing can be seen in a mirror because it is dark isn't correct from a real world perspective so I don't see why it should apply to creatures with Darkvision in a fantasy world.
1) Mirrors reflect light in a particular spectrum. This varies depending on the material the mirror is made from. The visible spectrum is typically 380-700 nanometer wavelengths. Near infra-red and infra-red are above 700nm while ultraviolet light lies below 380nm.
The following is a figure showing typical reflectance curves for a variety of metallic mirrors.
Depending on the material these extend beyond the wavelengths perceptible by the human eye.
2) Darkness is not the complete absence of light. It is an amount of light that is below the perception limit of the human eye or at wavelengths to which the eye is not sensitive. The human eye is very sensitive to light but there are still limits especially if the objective is to construct an image of what is seen. The human eye is composed of cones for colour vision and rods that provide visibility in low light conditions. The rods provide black and white vision.
Does a mirror work in darkness? Yes - if there are any photons present some of them will be reflected. These photons can be seen by a sensitive instrument. Light amplification goggles, IR goggles and UV goggles would be technological examples that provide vision at lower levels of light and into different parts of the spectrum.
How does Darkvision work? Who knows? :) It could simply be "magic" ... in which case the DM gets to decide if the "magic" of Darkvision gets to see reflections.
However, if Darkvision is based on a version of rods in the eye that are more sensitive than those in a human eye OR if Darkvision is based on viewing light in a different part of the spectrum (Infra red or near infra-red may be present even if visible light might not be) then there is really no physical reason to say that mirrors would not work.
IF there was a "complete absence of light" then a mirror would not work since there would be nothing to reflect. This might be the condition found within a Darkness spell where Darkvision is explicitly stated not to work (based on one interpretation of the Darkness spell). However, a complete absence of light is NOT just darkness - it goes well beyond that since infra-red and ultra-violet are also "light" - they are still part of the same spectrum just outside the range humans can usually perceive.
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The bottom line is that it is a DM call but the reasoning that a mirror doesn't work in the "dark" is flawed unless there really are NO photons - in which case Darkvision wouldn't work either unless it was a magical ability.
How does Darkvision work? Who knows? :) It could simply be "magic" ... in which case the DM gets to decide if the "magic" of Darkvision gets to see reflections.
Darkvision as written is magic; it can't be a non-visual spectrum because it's usable to read written materials (inks are not necessarily visible outside of the visual band, and you have to push pretty deep into the infrared spectrum to be able to see without a light source) and the light level inside a deep cave or dungeon rapidly drops to the point where photon counts are too low to permit imaging. Not to mention that range limits on vision are nonsense.
The dark vision trait in 5E does not dictate any issues other than color when using dark vision. I’ve even seen dungeons with no light sources mention reflection.
The question is not whether Darkvision says no reflections, but whether it ALLOWS for reflection. You are presuming the question.
In the game, everything is assumed to follow normal physics EXCEPT where the rules differ. No where in the game does it say that normal people can't shoot laser beams out of their eyes, obviously they cannot unless something says it does.
Reflections are about light. (American Heritage definition: "Something, such as light, radiant heat, sound, or an image, that is reflected.") Without light, heat, sound or similar effect in the real world, there is no reflection. Therefore if there is no light, there is no reflection in the game as well, unless the game says otherwise or at least makes some mention of heat, sound or similar effect.
There is nothing about darkvision that states it can see reflections, nor any mention of heat, sound, etc. therefore you do not.
You are assuming dark vision is like its predecessor infravision.
Darkvision
Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
Assuming one has dark vision in a place of complete darkness, their dark vision trait allows them to see as if they are in dim light.
Dim light, also called shadows, creates a lightly obscured area. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light.
Using your real world physics (keep your reality out of my fantasy game) go outside during a full moon with small mirror and tell me if you can see your reflection. What I'm getting at, if the rules don't say specifically that something reasonable can't be done then it is allowed by RAW. After all how many still believe that a Natural 1 is a critical fail on ability or saving throws (not including death saves) or that a Natural 20 is an auto success on those same rolls?
in complete darkness miroirs have nothing to reflect regardless if one can see in darkness or not.
The issue for me is; how does darkvision actually work? This is never explained in the game, we're only told what it does from a mechanical perspective.
If we extrapolate from that, what darkvision is doing is allowing us to treat areas of an environment as one light level brighter than they actually are, but without colour.
This means that when a creature with darkvision is in an area of total darkness they treat it as dim light, i.e- as if there were some light, albeit not carrying any colour. So for all intents and purposes that area is dimly lit for them, so there is definitely an argument to be made that a mirror would still work as whatever light (or not quite light) that they are seeing by presumably functions as light normally would, even if it's not visible to anyone else. We see this in nature with birds, insects etc. that can see ultraviolet light, able to respond to things that nothing else can see (and sometimes even in darkness, when that ultraviolet light is given off as a result of chemical reaction).
With that in mind, it's worth considering that mirrors do not reflect only visible light; they can reflect infrared, ultraviolet etc. so whatever it is that a creature with darkvision can see in darkness, it's reasonable to assume that a mirror might also reflect it in the same way as light, because for creatures with darkvision there effectively is light from the mechanical perspective. Whether it's something magical or not, it behaves like light for them, so it's not unreasonable to assume that it would reflect in the same way as normal light does.
Lastly, darkvision is really just the same as the darkvision that we all have; i.e- when you let your eyes adjust to the dark you can see in low light better, but it's harder to distinguish colours. This fantasy darkvision is a superior version that works in even darker areas.
But this is fully within DM fiat; all we have are the mechanics, with no proper explanation of how it's supposed to work beyond that.
The final point I think is that functionally speaking if there are two rulings, none of which is solidly backed up in RAW, the "correct" answer is usually the one that makes most sense in terms of keeping the game going; if a player with darkvision wants to see a reflection in a mirror, then I'd personally allow it because it's better than getting into a lengthy debate about whether or not that would work, especially when there are no balance issues with it (it's still just letting them see as if in dim light, which is what darkvision is for).
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I always thought of darkvision as a mish-mash of infravision and ultravision from 1e, only very much simplified for the sake of 5e theme.
3e replaced Infravision and Ultravision with Darkvision and Night Vision, I think on the theory that they were excessively SF concepts for a fantasy game, plus understanding what you could actually detect with those senses was difficult for DMs and players.
The fact that darkvision allows you see in darkness as if it were dim light suggests that you can see reflections in mirrors, since anyone can see reflections in a mirror in dim light.
Any discussion about real world physics can be ignored, because of ... it's a fantasy world with magic and other weird stuff happening.
in complete darkness miroirs have nothing to reflect regardless if one can see in darkness or not.
The issue for me is; how does darkvision actually work? This is never explained in the game, we're only told what it does from a mechanical perspective.
If we extrapolate from that, what darkvision is doing is allowing us to treat areas of an environment as one light level brighter than they actually are, but without colour.
This means that when a creature with darkvision is in an area of total darkness they treat it as dim light, i.e- as if there were some light, albeit not carrying any colour.
To me darkvision doesnt create dim light it let you see as it it was. Mirror has nohing to do with vision, it only care about light which if there is none wont have any reflect. Darkvision alone doesnt create light refletion in miroir.
Same thing with shadows. Without light there is no shadow cast even if you can see in darkness as if it was dim light.
To me darkvision doesnt create dim light it let you see as it it was. Mirror has nohing to do with vision, it only care about light which if there is none wont have any reflect. Darkvision alone doesnt create light refletion in miroir.
If you can see in darkness as if it were dim light then that means there must be something to see by. Whatever that might be, whether it's just very weak light, or some other form of radiation that other creatures can't see, there's no reason to immediately assume that a mirror would not reflect it the same as any other light, as most mirrors do reflect things that we humans cannot see.
For example, humans cannot see infrared light, but most mirrors will reflect it just as effectively as any other light, same with ultraviolet. Something that can see infrared or ultraviolet will see these as reflections in a mirror, same as we would see visible light, and these would cast shadows.
Same thing with shadows. Without light there is no shadow cast even if you can see in darkness as if it was dim light.
Shadows is an interesting case given the way in which darkvision works; because it universally treats darkness as dim light, then we can assume whatever a creature with darkvision sees by isn't in the environment normally (otherwise it would make shadows of its own, even to darkvision).
This makes it possible that whatever a creature sees by is also provided by themselves, e.g- think of it like a nightvision security camera that has its own infrared light source; this bathes everything in its vision with light that only it can see, but if there is a mirror within that area, the light still scatters and so the night vision camera will still see a reflection (as long as the IR bounces off the mirror, hits something and then bounces back to the camera). To me this is the closest real world analogue we can possibly have.
But that's also an incredibly complicated way to resolve it; the simplest path in rules terms is that the rule says treat darkness like dim light, mirrors work in dim light, ergo mirrors work for a creature with darkvision. It's not super well supported in Rules As Written but it's IMO the cleaner path than mirrors don't work, both in rules terms and functionally. If anything mirrors not working would need to be defined in the rules, because it sounds like an exception to what darvision actually says, plus mirrors in D&D are never defined as only functioning if there's light (nor are they in reality, as they do still reflect even in the total absence of light, it's just going to be things we can't see).
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For example, humans cannot see infrared light, but most mirrors will reflect it just as effectively as any other light, same with ultraviolet. Something that can see infrared or ultraviolet will see these as reflections in a mirror, same as we would see visible light, and these would cast shadows.
See, that kind of thing is why they decided to get rid of infravision. Most mirrors are not going to reflect thermal IR (they might reflect near IR, but that's kind of useless).
If you think it works as a light amplifier (aka the green fuzzy images: https://www.military.com/equipment/pvs-14), then yes, it reflects off of mirrors. All it is doing is amplifying the available "visible" light spectrum to levels that can be seen by the eye.
If you think it works like thermal vision (aka the black and white or multi-colored images that see heat: https://botach.com/l3-lwts-handheld-clip-on-thermal-weapon-sight/), then that wavelength behaves differently. Glass that is transparent to visible light is reflective to infrared light. A mirror would be reflective, but its reflecting off the glass, not the mirrored backplane, but so would a window (you can't see through it in thermal).
"This makes it possible that whatever a creature sees by is also provided by themselves, e.g- think of it like a nightvision security camera that has its own infrared light source; this bathes everything in its vision with light that only it can see,"
If the creature casting out the "light" it uses to see by then every other creature that uses the same ability would see them like flashlights in a cave. This is the reason that military's around the world no linger use IR lamps to drive by.
"This makes it possible that whatever a creature sees by is also provided by themselves, e.g- think of it like a nightvision security camera that has its own infrared light source; this bathes everything in its vision with light that only it can see,"
If the creature casting out the "light" it uses to see by then every other creature that uses the same ability would see them like flashlights in a cave. This is the reason that military's around the world no linger use IR lamps to drive by.
I'm not saying that's exactly how it works, I'm saying that's the closest comparison we have to how it might work; darkvision is something not quite like the things we're familiar with. Maybe the creatures create their own "light" but it's special light only detectable by themselves?
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can see in dim light within the radius as if it were bright light, and in darkness as if it were dim light
It therefor stands to reason, because you could see images reflected in a mirror in dim light, you can see images reflected in a mirror in darkness with darkvision because you see as if it were dim light.
The how would be something decided by the table, which is generally how these kinds of mechanical implication oddities should ideally be resolved. The rules state a certain thing happens, and then it's down to the group to resolve how that works. Maybe darkvision always assumes theres at least some light everywhere and darkvision amplifies that? Maybe darkvision just uses magical intent and allows you to see in a mirror via that?
It seems obvious to me, that darkvision is just what nocturnal creatures like owls have. They can see... In the dark. Generally, there's not enough darkness to make them blind in the real world. You could achieve such darkness using magic. (Or a totally sealed container. Or the inside of a froghemoth!)
Devil's Sight is different. That's the one that's actually weird. How does it work? Who knows. I like to imagine they emit evil beams that reflect back to them. Paladins can see these evil beams of course.
But regular darkvision, that would work with mirrors just fine, because all is doing is making you more sensitive to the small amount of light that there actually is in most dark environments.
Devil's Sight is different. That's the one that's actually weird. How does it work? Who knows. I like to imagine they emit evil beams that reflect back to them. Paladins can see these evil beams of course.
This is a great question. If magical Darkness is a total absence of all light, then a mirror should not "work" as a reflective surface in that situation. The problem is that magical darkness is not explained either.
Now, to the OP's question, I could see an interesting scenario wherein a creature with Darkvision wanders into a crystal cave or something with a lot of reflective surfaces, but no sources of light, then gets ambushed by a vampire since it's Dracula lore that vampires cannot be seen in normal mirrors.
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id say no réflection in miroir can be seen whatsoever in complete absence of light.
As long as the rules do not say how Darkvision works, it is entirely up to the DM to decide whether reflections are visible for a creature with Darkvision. Personally, I would rule that reflections can be seen by a creature with Darkvision.
However, the statement that nothing can be seen in a mirror because it is dark isn't correct from a real world perspective so I don't see why it should apply to creatures with Darkvision in a fantasy world.
1) Mirrors reflect light in a particular spectrum. This varies depending on the material the mirror is made from. The visible spectrum is typically 380-700 nanometer wavelengths. Near infra-red and infra-red are above 700nm while ultraviolet light lies below 380nm.
The following is a figure showing typical reflectance curves for a variety of metallic mirrors.
https://www.edmundoptics.com/contentassets/f4d2957407f247f68c1965eb4c2c5df2/fig-4-mmcv2.png
Depending on the material these extend beyond the wavelengths perceptible by the human eye.
2) Darkness is not the complete absence of light. It is an amount of light that is below the perception limit of the human eye or at wavelengths to which the eye is not sensitive. The human eye is very sensitive to light but there are still limits especially if the objective is to construct an image of what is seen. The human eye is composed of cones for colour vision and rods that provide visibility in low light conditions. The rods provide black and white vision.
Does a mirror work in darkness? Yes - if there are any photons present some of them will be reflected. These photons can be seen by a sensitive instrument. Light amplification goggles, IR goggles and UV goggles would be technological examples that provide vision at lower levels of light and into different parts of the spectrum.
How does Darkvision work? Who knows? :) It could simply be "magic" ... in which case the DM gets to decide if the "magic" of Darkvision gets to see reflections.
However, if Darkvision is based on a version of rods in the eye that are more sensitive than those in a human eye OR if Darkvision is based on viewing light in a different part of the spectrum (Infra red or near infra-red may be present even if visible light might not be) then there is really no physical reason to say that mirrors would not work.
IF there was a "complete absence of light" then a mirror would not work since there would be nothing to reflect. This might be the condition found within a Darkness spell where Darkvision is explicitly stated not to work (based on one interpretation of the Darkness spell). However, a complete absence of light is NOT just darkness - it goes well beyond that since infra-red and ultra-violet are also "light" - they are still part of the same spectrum just outside the range humans can usually perceive.
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The bottom line is that it is a DM call but the reasoning that a mirror doesn't work in the "dark" is flawed unless there really are NO photons - in which case Darkvision wouldn't work either unless it was a magical ability.
if there is any presence of light, as minimal as it can be, a miroir will reflect it this is unquetionable. The question is when there's none.
in complete darkness miroirs have nothing to reflect regardless if one can see in darkness or not.
How do the Drow see a mile below ground?
The darkness spell works on them.
Darkvision as written is magic; it can't be a non-visual spectrum because it's usable to read written materials (inks are not necessarily visible outside of the visual band, and you have to push pretty deep into the infrared spectrum to be able to see without a light source) and the light level inside a deep cave or dungeon rapidly drops to the point where photon counts are too low to permit imaging. Not to mention that range limits on vision are nonsense.
You are assuming dark vision is like its predecessor infravision.
Darkvision
Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
Assuming one has dark vision in a place of complete darkness, their dark vision trait allows them to see as if they are in dim light.
Dim light, also called shadows, creates a lightly obscured area. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light.
Using your real world physics (keep your reality out of my fantasy game) go outside during a full moon with small mirror and tell me if you can see your reflection. What I'm getting at, if the rules don't say specifically that something reasonable can't be done then it is allowed by RAW. After all how many still believe that a Natural 1 is a critical fail on ability or saving throws (not including death saves) or that a Natural 20 is an auto success on those same rolls?
The issue for me is; how does darkvision actually work? This is never explained in the game, we're only told what it does from a mechanical perspective.
If we extrapolate from that, what darkvision is doing is allowing us to treat areas of an environment as one light level brighter than they actually are, but without colour.
This means that when a creature with darkvision is in an area of total darkness they treat it as dim light, i.e- as if there were some light, albeit not carrying any colour. So for all intents and purposes that area is dimly lit for them, so there is definitely an argument to be made that a mirror would still work as whatever light (or not quite light) that they are seeing by presumably functions as light normally would, even if it's not visible to anyone else. We see this in nature with birds, insects etc. that can see ultraviolet light, able to respond to things that nothing else can see (and sometimes even in darkness, when that ultraviolet light is given off as a result of chemical reaction).
With that in mind, it's worth considering that mirrors do not reflect only visible light; they can reflect infrared, ultraviolet etc. so whatever it is that a creature with darkvision can see in darkness, it's reasonable to assume that a mirror might also reflect it in the same way as light, because for creatures with darkvision there effectively is light from the mechanical perspective. Whether it's something magical or not, it behaves like light for them, so it's not unreasonable to assume that it would reflect in the same way as normal light does.
Lastly, darkvision is really just the same as the darkvision that we all have; i.e- when you let your eyes adjust to the dark you can see in low light better, but it's harder to distinguish colours. This fantasy darkvision is a superior version that works in even darker areas.
But this is fully within DM fiat; all we have are the mechanics, with no proper explanation of how it's supposed to work beyond that.
The final point I think is that functionally speaking if there are two rulings, none of which is solidly backed up in RAW, the "correct" answer is usually the one that makes most sense in terms of keeping the game going; if a player with darkvision wants to see a reflection in a mirror, then I'd personally allow it because it's better than getting into a lengthy debate about whether or not that would work, especially when there are no balance issues with it (it's still just letting them see as if in dim light, which is what darkvision is for).
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I always thought of darkvision as a mish-mash of infravision and ultravision from 1e, only very much simplified for the sake of 5e theme.
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3e replaced Infravision and Ultravision with Darkvision and Night Vision, I think on the theory that they were excessively SF concepts for a fantasy game, plus understanding what you could actually detect with those senses was difficult for DMs and players.
The fact that darkvision allows you see in darkness as if it were dim light suggests that you can see reflections in mirrors, since anyone can see reflections in a mirror in dim light.
Any discussion about real world physics can be ignored, because of ... it's a fantasy world with magic and other weird stuff happening.
To me darkvision doesnt create dim light it let you see as it it was. Mirror has nohing to do with vision, it only care about light which if there is none wont have any reflect. Darkvision alone doesnt create light refletion in miroir.
Same thing with shadows. Without light there is no shadow cast even if you can see in darkness as if it was dim light.
If you can see in darkness as if it were dim light then that means there must be something to see by. Whatever that might be, whether it's just very weak light, or some other form of radiation that other creatures can't see, there's no reason to immediately assume that a mirror would not reflect it the same as any other light, as most mirrors do reflect things that we humans cannot see.
For example, humans cannot see infrared light, but most mirrors will reflect it just as effectively as any other light, same with ultraviolet. Something that can see infrared or ultraviolet will see these as reflections in a mirror, same as we would see visible light, and these would cast shadows.
Shadows is an interesting case given the way in which darkvision works; because it universally treats darkness as dim light, then we can assume whatever a creature with darkvision sees by isn't in the environment normally (otherwise it would make shadows of its own, even to darkvision).
This makes it possible that whatever a creature sees by is also provided by themselves, e.g- think of it like a nightvision security camera that has its own infrared light source; this bathes everything in its vision with light that only it can see, but if there is a mirror within that area, the light still scatters and so the night vision camera will still see a reflection (as long as the IR bounces off the mirror, hits something and then bounces back to the camera). To me this is the closest real world analogue we can possibly have.
But that's also an incredibly complicated way to resolve it; the simplest path in rules terms is that the rule says treat darkness like dim light, mirrors work in dim light, ergo mirrors work for a creature with darkvision. It's not super well supported in Rules As Written but it's IMO the cleaner path than mirrors don't work, both in rules terms and functionally. If anything mirrors not working would need to be defined in the rules, because it sounds like an exception to what darvision actually says, plus mirrors in D&D are never defined as only functioning if there's light (nor are they in reality, as they do still reflect even in the total absence of light, it's just going to be things we can't see).
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See, that kind of thing is why they decided to get rid of infravision. Most mirrors are not going to reflect thermal IR (they might reflect near IR, but that's kind of useless).
For simplicity, yes. In physics terms, maybe?
It depends how you interpret darkvision to work.
If you think it works as a light amplifier (aka the green fuzzy images: https://www.military.com/equipment/pvs-14), then yes, it reflects off of mirrors. All it is doing is amplifying the available "visible" light spectrum to levels that can be seen by the eye.
If you think it works like thermal vision (aka the black and white or multi-colored images that see heat: https://botach.com/l3-lwts-handheld-clip-on-thermal-weapon-sight/), then that wavelength behaves differently. Glass that is transparent to visible light is reflective to infrared light. A mirror would be reflective, but its reflecting off the glass, not the mirrored backplane, but so would a window (you can't see through it in thermal).
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"This makes it possible that whatever a creature sees by is also provided by themselves, e.g- think of it like a nightvision security camera that has its own infrared light source; this bathes everything in its vision with light that only it can see,"
If the creature casting out the "light" it uses to see by then every other creature that uses the same ability would see them like flashlights in a cave. This is the reason that military's around the world no linger use IR lamps to drive by.
I'm not saying that's exactly how it works, I'm saying that's the closest comparison we have to how it might work; darkvision is something not quite like the things we're familiar with. Maybe the creatures create their own "light" but it's special light only detectable by themselves?
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The wording for darkvision says:
It therefor stands to reason, because you could see images reflected in a mirror in dim light, you can see images reflected in a mirror in darkness with darkvision because you see as if it were dim light.
The how would be something decided by the table, which is generally how these kinds of mechanical implication oddities should ideally be resolved. The rules state a certain thing happens, and then it's down to the group to resolve how that works. Maybe darkvision always assumes theres at least some light everywhere and darkvision amplifies that? Maybe darkvision just uses magical intent and allows you to see in a mirror via that?
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Just assume there is always some trickle of bio-luminescence in caves and tunnels.
That only total darkness is caused by the spell or spell effect. Or special situations explained by the DM.
The only real argument I have about it is the different distances each race can view. They should all be able to see as far as normal vision.
It seems obvious to me, that darkvision is just what nocturnal creatures like owls have. They can see... In the dark. Generally, there's not enough darkness to make them blind in the real world. You could achieve such darkness using magic. (Or a totally sealed container. Or the inside of a froghemoth!)
Devil's Sight is different. That's the one that's actually weird. How does it work? Who knows. I like to imagine they emit evil beams that reflect back to them. Paladins can see these evil beams of course.
But regular darkvision, that would work with mirrors just fine, because all is doing is making you more sensitive to the small amount of light that there actually is in most dark environments.
This is a great question. If magical Darkness is a total absence of all light, then a mirror should not "work" as a reflective surface in that situation. The problem is that magical darkness is not explained either.
Now, to the OP's question, I could see an interesting scenario wherein a creature with Darkvision wanders into a crystal cave or something with a lot of reflective surfaces, but no sources of light, then gets ambushed by a vampire since it's Dracula lore that vampires cannot be seen in normal mirrors.