A mirror can be an extremely powerful tool in the hands of a spellcaster. Many spells only require that you see your target. Just hide behind total cover and use a mirror. Just remember that using a mirror in this way counts as your free action and that the mirror itself has an AC of 19 and 5 (2d4) hit points.
EDIT: After much debate, this trick was unfortunately debunked according to the RAW. Thank you everyone who participated in this debate. I came to this conclusion on post #19.
A mirror can be an extremely powerful tool in the hands of a spellcaster. Many spells only require that you see your target. Just hide behind total cover and use a mirror. Just remember that using a mirror in this way counts as your free action and that the mirror itself has an AC of 19 and 5 (2d4) hit points.
A target has total cover if it is completely concealed by an obstacle. This means if you can see a target via a mirror, it can generally see the limb you are holding the mirror with. It is nearly but not completely impossible to be in total cover while a mirror is letting you see something.
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. This means almost no spells will work the way you're describing, because almost all of them are hard stopped by total cover, regardless of being able to see your target. The only spells that will work like you're describing have to initially target something other than what you want to hit with the spell (or nothing at all), so that when they subsequently target what you want to enspell (or if the spell doesn't do any secondary targeting, either), the above rule doesn't apply. For example, you could cast Fireball this way, using the mirror to determine where your enemy is, then casting Fireball at a point in space which you don't have total cover relative to, so that the spell's AOE clips the creature you want dead. A significantly more commonly used example is that you can Misty Step to a point you can only see via a mirror, because Misty Step targets the caster, not the destination.
From a simplicity standpoint, why not just step out, cast the spell, then step back in to toal cover?
From a game standpoint, there are no rules for exposing only part of the body. If any part of a character (including the items they are holding and/or carrying) is visible, then the character is visible for the purposes of targeting. If a character has a mirror poking out from cover and a foes sucessfully attacks then the character takes damage.
From a simplicity standpoint, why not just step out, cast the spell, then step back in to toal cover?
From a game standpoint, there are no rules for exposing only part of the body. If any part of a character (including the items they are holding and/or carrying) is visible, then the character is visible for the purposes of targeting. If a character has a mirror poking out from cover and a foes sucessfully attacks then the character takes damage.
If you are in LOS when casting the spell you will trigger reactions if present. Now you can use the ready action to prevent that for example you cannot counterspell a readied spell unless you saw it being readied but that also costs a reaction and concentration.
A mirror can be an extremely powerful tool in the hands of a spellcaster. Many spells only require that you see your target. Just hide behind total cover and use a mirror. Just remember that using a mirror in this way counts as your free action and that the mirror itself has an AC of 19 and 5 (2d4) hit points.
A target has total cover if it is completely concealed by an obstacle. This means if you can see a target via a mirror, it can generally see the limb you are holding the mirror with. It is nearly but not completely impossible to be in total cover while a mirror is letting you see something.
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. This means almost no spells will work the way you're describing, because almost all of them are hard stopped by total cover, regardless of being able to see your target. The only spells that will work like you're describing have to initially target something other than what you want to hit with the spell (or nothing at all), so that when they subsequently target what you want to enspell (or if the spell doesn't do any secondary targeting, either), the above rule doesn't apply. For example, you could cast Fireball this way, using the mirror to determine where your enemy is, then casting Fireball at a point in space which you don't have total cover relative to, so that the spell's AOE clips the creature you want dead. A significantly more commonly used example is that you can Misty Step to a point you can only see via a mirror, because Misty Step targets the caster, not the destination.
I think the cover rules are iffy personally. You can read them two ways
only sight is necessary. This is based on common usage of the word concealed
If it is the former you can cast if you have the mirror out and they can cast back if they can see the mirror.
If it's the later then you can't cast through a mirror and they cant cast back at you through it.
I don't know any ruling that would allow you to cast through the mirror but not enemies but it would prevent attacks and you could conceivably drop the mirror after using it preventing it being used against you.
We always assumed there was a large difference between seeing our head pocking around a corner vs a 4 square inch mirror poking around a corner.
You can not cast a spell off of one. But spells like true sight cast on you would work with a mirror.
We also added a stick like handle to the mirror for ease of use.
We use them to look under doors if there is a little space under the door to see through. Or over walls and objects.
Plus they might help with your disguise skill.
You could also hang one on a string from a tree to reflect light and flash for quite a distance. Makes a good daytime distraction for those guys following you.
But like normal, things like this are quite situational.
A target has total cover if it is completely concealed by an obstacle. This means if you can see a target via a mirror, it can generally see the limb you are holding the mirror with. It is nearly but not completely impossible to be in total cover while a mirror is letting you see something.
From a simplicity standpoint, why not just step out, cast the spell, then step back in to toal cover?
From a game standpoint, there are no rules for exposing only part of the body. If any part of a character (including the items they are holding and/or carrying) is visible, then the character is visible for the purposes of targeting. If a character has a mirror poking out from cover and a foes sucessfully attacks then the character takes damage.
Like Solarsyphon stated, that would allow the enemy to use their reaction, including after a ready action, to attack you during your turn. I actually thought about that when making this thread.
I'm not entirely convinced. I believe the target would be the item, not the creature. This is why I specified the mirror's AC and hit points.
If it is the former you can cast if you have the mirror out and they can cast back if they can see the mirror. If it's the later then you can't cast through a mirror and they cant cast back at you through it. I don't know any ruling that would allow you to cast through the mirror but not enemies but it would prevent attacks and you could conceivably drop the mirror after using it preventing it being used against you.
Honestly, this is the kind of thing Sage Advice should answer. Can someone do it in my stead? I don't use Twitter. And you're right about moving the mirror out of the way after casting the spell. If my trick works according to the rules, then an enemy could do the same to you by using their reaction at the exact moment you use the mirror.
We always assumed there was a large difference between seeing our head pocking around a corner vs a 4 square inch mirror poking around a corner. You can not cast a spell off of one. But spells like true sight cast on you would work with a mirror.
I'm not talking about casting a spell off of a mirror but to simply abide by the RAW. When a spell says that you need to see your target, then you only need to see it to target it. Let's take the cantrip sacred flame for example. As long as your target is within 60 feet of you and that you can see it, you may target it regardless of cover. Your target could be completely encased in a cube made of glass and it would still be affected. If you need to explain it narratively, then you can assume that a) the flame-like radiance goes through the glass or that b) it materializes inside of the cube. EDIT: This is actually incorrect. See post #17 for an explanation.
I'm wondering how this would differ from just getting behind cover.... and on your turn peak over the cover, cast your spell, then duck behind cover again.
Many spells require a line of sight. A straight line from the caster to the target. Not just seeing the target, otherwise scrying would always allow you to cast a spell to the target not counting spell range.
As for the glass box theory. If you could not cast through glass for sacred flame or even Flame Strike then you could not cast those spells at anytime indoors. Or else a simple umbrella would protect the targets.
From a simplicity standpoint, why not just step out, cast the spell, then step back in to toal cover?
From a game standpoint, there are no rules for exposing only part of the body. If any part of a character (including the items they are holding and/or carrying) is visible, then the character is visible for the purposes of targeting. If a character has a mirror poking out from cover and a foes sucessfully attacks then the character takes damage.
When a player does that in one of my games, what I do is save action until it shows up. You have to be fair, and set a clear trigger, of course. But with this tactic you make a player not feel invulnerable and have to adapt his tactics. If not, the game becomes boring.
If someone did the mirror thing to me (putting a stick on it or whatever), I'd find a way to mess up their tactic. These things, when a player abuses them, make the game very boring as the player doesn't feel the pressure of death that he should feel in combat.
"Line of sight" is literally a line. If you can't draw a straight line to your target, your target is considered behind total cover. Using a mirror to peek around a corner might give you a PER check to see what's there, but it won't let you target that thing with a spell
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.
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.
A basic 5 gp item in the PHB doesn't allow you to get around that rule, and doesn't give you the same advantages as a 4th-level spell
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I'm wondering how this would differ from just getting behind cover.... and on your turn peak over the cover, cast your spell, then duck behind cover again.
Please read each post before commenting. This has been discussed already.
Many spells require a line of sight. A straight line from the caster to the target. Not just seeing the target, otherwise scrying would always allow you to cast a spell to the target not counting spell range.
And? I clearly said in the OP that the mirror trick only works with spells that only require you to see your target.
If someone did the mirror thing to me (putting a stick on it or whatever), I'd find a way to mess up their tactic. These things, when a player abuses them, make the game very boring as the player doesn't feel the pressure of death that he should feel in combat.
Hence why I specified the mirror's AC and hit points. A smart enemy can use the ready action to target the mirror as it is brandished, potentially destroying it. An enemy spellcaster can also ready its own spell that requires seeing its target to attack the player as they brandish their mirror. An enemy may also hide behind cover, making itself unseen and forcing a stalemate. Even a stupid enemy knows to move around the cover and attack the player in melee. Nothing about my mirror trick is gamebreaking.
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all spells require a line of sight unless otherwise stated. A clear line from caster to target. How many require ONLY seeing the target?
I'm not going to go through the hundreds of spells available to give you a number, especially considering the fact that most of them don't even say anything about "line of sight". I'll just give you an example: Sacred Flame. But you're asking the wrong question. What you should be asking is how many spells don't require a straight line to the target. Let's take the following spell: Flame Strike. It doesn't even require you to see anything. You just specify a location (not even a point) within range and that's it. It doesn't say anything about cover, but Sage Advice says that it can be cast indoors, so that means it ignores cover.
What you're referring to as "line of sight" is actually the rule on having a clear path to the target. Unless otherwise specified, a clear path doesn't have to be a straight line. If you're looking at someone via a mirror, it's still within your line of sight. Line of sight doesn't have to be a straight line. If you can see your target, it means that there's nothing obstructing the path between you and your target. The only exception is if there's a transparent obstacle into the equation. Although you can see your target encased inside a glass cube, that glass counts as cover. You need a clear path to throw a rock at someone. If there's a wall but no ceiling between you and your target, nothing stops you from throwing the rock above the wall and have it land on your target, although it's easy to argue that this would be done with disadvantage. That's what a clear path is.
The only question that remains is whether or not your target benefits from total cover when using my mirror trick. The rules say that a target with total cover can't be targeted directly by an attack or a spell, but I don't think the target from my trick is actually benefiting from total cover. If it did, then that would mean throwing a rock above an obstacle and have it land on your target is impossible. That clearly makes no sense, so this is why my mirror trick should work. It could be argued that, depending on what the spell says, the target should have a bonus to its AC or Dexterity saving throw.
A typical spell requires you to pick one or more targets to be affected by the spell’s magic. A spell’s description tells you whether the spell targets creatures, objects, or a point of origin for an area of effect (described below).
Unless a spell has a perceptible effect, a creature might not know it was targeted by a spell at all. An effect like crackling lightning is obvious, but a more subtle effect, such as an attempt to read a creature’s thoughts, typically goes unnoticed, unless a spell says otherwise.
A Clear Path to the Target
To target something, you must have a clear path to it, so it can’t be behind total cover.
If you place an area of effect at a point that you can’t see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction.
A mirror does not remove an obstruction between you and a target -- whether that target is a creature or a point in space for an AoE. It might let you see it, but that doesn't mean you can target it with a spell
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If you can see a target by using a mirror, it is no longer behind total cover.
This is simply not true. If you can see a creature around the corner of a bending corridor 15 feet away from you, your arrow doesn't bend around the corner as you shoot, neither does it pass through the wall to hit your target.
If you can see a target by using a mirror, it is no longer behind total cover.
This is simply not true. If you can see a creature around the corner of a bending corridor 15 feet away from you, your arrow doesn't bend around the corner as you shoot, neither does it pass through the wall to hit your target.
But we're not talking about bows and arrows here. The fact that you can see your target via a mirror means that there's a clear path to it. Spells aren't bows and arrows. Unless it specifies that it requires a straight line, spells can bend and seek their target; some don't even have to because they aren't tangible, they just magically cause the target to suffer an effect. Are you actually going to tell me that there's no way for a thrown rock to lob over an obstacle and land on a target? Since when are straight lines an absolute necessity for everything? Heck, not even bows and arrows require a straight line. Arrows are affected by gravity. Real life archers aim for the sky when combating an army. They have to consider gravity and the wind, so they're always aiming above their target and adjusting their angle. Heck, the same actually applies with firearms. Snipers don't actually shoot in a straight line. Bullets are affected by gravity and the wind just like any other projectile. Are you going to tell me that because there are no straight line between the attacker and the target, it's impossible to hit it with any projectile?
Do you actually believe that a spell like charm person can only work if there's a straight line between the caster and the target? As long as your target is within range and you can see it, it works. Besides, half cover and three-quarters cover only affect spells that require a Dexterity saving throw, although some spells like sacred flame clearly specify that they ignore cover. Total cover is different, as it does prevent spells from directly targeting something. Sage Advice says that a spell such as charm person can be blocked by a glass window. But the RAW makes it clear: a target has total cover if it is completely concealed by an obstacle. In a scenario where your target is encased inside a glass cube, it is completely concealed by an obstacle. When I think about it more, what I previously said regarding sacred flame working in that scenario is wrong. It only says that the target gains no benefit from cover for their Dexterity saving throw, but total cover doesn't care. If you aren't allowed to target the thing inside that glass cube, it's simply not affected by the spell; no saving throw is required.
However, it becomes a different story if there's a hole in that glass cube. The latter suddenly becomes three-quarters cover because at least three-quarters of the target is covered and the target isn't completely concealed. In my mirror trick scenario, cover is relative. The caster has total cover from the target but the target doesn't have total cover from the caster. You can't say that the target is completely concealed because the caster can clearly see it and there's a clear path to it. As I explained before, a clear path doesn't have to be a straight line. You could draw a (non straight) line between the caster and the target. No barrier is preventing that line from reaching its target. In other words, the target doesn't benefit from total cover unless the spell specifies that it requires a straight line.
This at least works in theory. Someone needs to ask Sage Advice for clarification.
If you can see a target by using a mirror, it is no longer behind total cover.
This is simply not true. If you can see a creature around the corner of a bending corridor 15 feet away from you, your arrow doesn't bend around the corner as you shoot, neither does it pass through the wall to hit your target.
But we're not talking about bows and arrows here. The fact that you can see your target via a mirror means that there's a clear path to it. Spells aren't bows and arrows. Unless it specifies that it requires a straight line, spells can bend and seek their target; some don't even have to because they aren't tangible, they just magically cause the target to suffer an effect.
Using a mirror to look around corners might grant you vision of the target, not a clear path. It is effectively the same as if you use the Scrying spell to look at someone in another room: you don't suddenly have a clear path to the target just because you can see it. The walls between you still exist. If you are holding your mirror in your own space, it grants you no special benefits as your point of view is the same. If you hold it on a stick so it protrudes into an adjacent space, then there might be a clear path between the mirror and the target. However you are not your mirror. If you don't move into the same space as the mirror, you still wouldn't have a clear path to your target. As you can see in the illustrations below, cover is measured from the attacker's space to the target's space.
Are you actually going to tell me that there's no way for a thrown rock to lob over an obstacle and land on a target? Since when are straight lines an absolute necessity for everything. Heck, not even bows and arrows require a straight line. Arrows are affected by gravity. Real life archers aim for the sky when combating an army. They have to consider gravity and the wind, so they're always aiming above their target and adjusting their angle. Heck, the same actually applies with firearms. Snipers don't actually shoot in a straight line. Bullets are affected by gravity and the wind just like any other projectile. Are you going to tell me that because there are no straight line between the attacker and the target, it's impossible to hit it with any projectile?
Yes, the rules don't take gravity into account for targeting purposes.
Do you actually believe that a spell like charm person can only work if there's a straight line between the caster and the target?
Yes, the targeting rules requires a clear path between the attacker and the target. How you describe it narratively is another matter. If you want an example of how a specific rule that allows an attack that bends, take a look at the Arcane Archer's Seeking Arrow below. Again this is a specific rule, not how the game generally works.
Seeking Arrow
Using divination magic, you grant your arrow the ability to seek out a target. When you use this option, you don’t make an attack roll for the attack. Instead, choose one creature you have seen in the past minute. The arrow flies toward that creature, moving around corners if necessary and ignoring three-quarters cover and half cover. If the target is within the weapon’s range and there is a path large enough for the arrow to travel to the target, the target must make a Dexterity saving throw. Otherwise, the arrow disappears after traveling as far as it can.
As long as your target is within range and you can see it, it works.
No, as long as you have a clear path to the target it works. And if the target is situated behind total cover, you don't have a clear path to the target.
Besides, half cover and three-quarters cover only affect spells that require a Dexterity saving throw, although some spells like sacred flame clearly specify that they ignore cover. Total cover is different, as it does prevent spells from directly targeting something. Sage Advice says that a spell such as charm person can be blocked by a glass window. But the RAW makes it clear: a target has total cover if it is completely concealed by an obstacle. In a scenario where your target is encased inside a glass cube, it is completely concealed by an obstacle. When I think about it more, what I previously said regarding sacred flame working in that scenario is wrong. It only says that the target gains no benefit from cover for their Dexterity saving throw, but total cover doesn't care. If you aren't allowed to target the thing inside that glass cube, it's simply not affected by the spell; no saving throw is required.
The spell description of Sacred Flame states that the target gains no benefit from cover for the spell's saving throw. What this means is that half cover would grant +2 to the dex save, three-quarters cover wouldn't grant +5 to the dex save, and full cover wouldn't prevent the caster from targeting the target. It doesn't mean the opposite. This is a specific rule, and specific rules beat general rules.
However, it becomes a different story if there's a hole in that glass cube. The latter suddenly becomes three-quarters cover because at least three-quarters of the target is covered and the target isn't completely concealed. In my mirror trick scenario, cover is relative. The caster has total cover from the target but the target doesn't have total cover from the caster. You can't say that the target is completely concealed because the caster can clearly see it and there's a clear path to it. As I explained before, a clear path doesn't have to be a straight line. You could draw a (non straight) line between the caster and the target. No barrier is preventing that line from reaching its target. In other words, the target doesn't benefit from total cover unless the spell specifies that it requires a straight line.
This at least works in theory. Someone needs to ask Sage Advice for clarification.
Again, being able to see someone and being able to target someone is not the same thing. Vision doesn't remove walls.
Thank you BeyondMisty for bringing some very good counterarguments to this debate.
Yes, the rules don't take gravity into account for targeting purposes.
Yeah, RAW sometimes make no sense. As a DM, I would still allow throwing a rock over an obstacle at disadvantage for 1d4 bludgeoning damage though. I would also rule throwing a non improvised weapon such as a javelin to only do 1d4 damage in this case, with the only difference being that it still adds the character's proficiency bonus to the attack roll. But in the case of a spell, I unfortunately really want to follow the RAW. Why? Because magic doesn't apply in real life, so I can't use real life logic.
The spell description of Sacred Flame states that the target gains no benefit from cover for the spell's saving throw. What this means is that half cover would grant +2 to the dex save, three-quarters cover wouldn't grant +5 to the dex save, and full cover wouldn't prevent the caster from targeting the target. It doesn't mean the opposite. This is a specific rule, and specific rules beat general rules.
Yes, that's basically what I meant, but thanks for putting it into other words to help other people understand it more.
Unless there's a spell that specifically bypasses the rules on total cover while still requiring seeing the target, I guess this really puts an end to my mirror trick. Does anyone know if such a spell even exist?
Unless there's a spell that specifically bypasses the rules on total cover while still requiring seeing the target, I guess this really puts an end to my mirror trick. Does anyone know if such a spell even exist?
Being able to bypass total cover and requiring you to be able to see the target are mutually exclusive, so there couldn't be a spell that did that.
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A mirror can be an extremely powerful tool in the hands of a spellcaster. Many spells only require that you see your target. Just hide behind total cover and use a mirror. Just remember that using a mirror in this way counts as your free action and that the mirror itself has an AC of 19 and 5 (2d4) hit points.
EDIT: After much debate, this trick was unfortunately debunked according to the RAW. Thank you everyone who participated in this debate. I came to this conclusion on post #19.
Age: 33 | Sex: Male | Languages: French and English | Roles: DM and Player
From a simplicity standpoint, why not just step out, cast the spell, then step back in to toal cover?
From a game standpoint, there are no rules for exposing only part of the body. If any part of a character (including the items they are holding and/or carrying) is visible, then the character is visible for the purposes of targeting. If a character has a mirror poking out from cover and a foes sucessfully attacks then the character takes damage.
If you are in LOS when casting the spell you will trigger reactions if present. Now you can use the ready action to prevent that for example you cannot counterspell a readied spell unless you saw it being readied but that also costs a reaction and concentration.
I think the cover rules are iffy personally. You can read them two ways
If it is the former you can cast if you have the mirror out and they can cast back if they can see the mirror.
If it's the later then you can't cast through a mirror and they cant cast back at you through it.
I don't know any ruling that would allow you to cast through the mirror but not enemies but it would prevent attacks and you could conceivably drop the mirror after using it preventing it being used against you.
We always assumed there was a large difference between seeing our head pocking around a corner vs a 4 square inch mirror poking around a corner.
You can not cast a spell off of one. But spells like true sight cast on you would work with a mirror.
We also added a stick like handle to the mirror for ease of use.
We use them to look under doors if there is a little space under the door to see through. Or over walls and objects.
Plus they might help with your disguise skill.
You could also hang one on a string from a tree to reflect light and flash for quite a distance. Makes a good daytime distraction for those guys following you.
But like normal, things like this are quite situational.
Honestly, this is the kind of thing Sage Advice should answer. Can someone do it in my stead? I don't use Twitter. And you're right about moving the mirror out of the way after casting the spell. If my trick works according to the rules, then an enemy could do the same to you by using their reaction at the exact moment you use the mirror.
I'm not talking about casting a spell off of a mirror but to simply abide by the RAW. When a spell says that you need to see your target, then you only need to see it to target it. Let's take the cantrip sacred flame for example. As long as your target is within 60 feet of you and that you can see it, you may target it regardless of cover.
Your target could be completely encased in a cube made of glass and it would still be affected. If you need to explain it narratively, then you can assume that a) the flame-like radiance goes through the glass or that b) it materializes inside of the cube.EDIT: This is actually incorrect. See post #17 for an explanation.Age: 33 | Sex: Male | Languages: French and English | Roles: DM and Player
I'm wondering how this would differ from just getting behind cover.... and on your turn peak over the cover, cast your spell, then duck behind cover again.
Many spells require a line of sight. A straight line from the caster to the target. Not just seeing the target, otherwise scrying would always allow you to cast a spell to the target not counting spell range.
As for the glass box theory. If you could not cast through glass for sacred flame or even Flame Strike then you could not cast those spells at anytime indoors. Or else a simple umbrella would protect the targets.
When a player does that in one of my games, what I do is save action until it shows up. You have to be fair, and set a clear trigger, of course. But with this tactic you make a player not feel invulnerable and have to adapt his tactics. If not, the game becomes boring.
If someone did the mirror thing to me (putting a stick on it or whatever), I'd find a way to mess up their tactic. These things, when a player abuses them, make the game very boring as the player doesn't feel the pressure of death that he should feel in combat.
"Line of sight" is literally a line. If you can't draw a straight line to your target, your target is considered behind total cover. Using a mirror to peek around a corner might give you a PER check to see what's there, but it won't let you target that thing with a spell
A basic 5 gp item in the PHB doesn't allow you to get around that rule, and doesn't give you the same advantages as a 4th-level spell
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Please read each post before commenting. This has been discussed already.
And? I clearly said in the OP that the mirror trick only works with spells that only require you to see your target.
Hence why I specified the mirror's AC and hit points. A smart enemy can use the ready action to target the mirror as it is brandished, potentially destroying it. An enemy spellcaster can also ready its own spell that requires seeing its target to attack the player as they brandish their mirror. An enemy may also hide behind cover, making itself unseen and forcing a stalemate. Even a stupid enemy knows to move around the cover and attack the player in melee. Nothing about my mirror trick is gamebreaking.
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all spells require a line of sight unless otherwise stated. A clear line from caster to target. How many require ONLY seeing the target?
I'm not going to go through the hundreds of spells available to give you a number, especially considering the fact that most of them don't even say anything about "line of sight". I'll just give you an example: Sacred Flame. But you're asking the wrong question. What you should be asking is how many spells don't require a straight line to the target. Let's take the following spell: Flame Strike. It doesn't even require you to see anything. You just specify a location (not even a point) within range and that's it. It doesn't say anything about cover, but Sage Advice says that it can be cast indoors, so that means it ignores cover.
What you're referring to as "line of sight" is actually the rule on having a clear path to the target. Unless otherwise specified, a clear path doesn't have to be a straight line. If you're looking at someone via a mirror, it's still within your line of sight. Line of sight doesn't have to be a straight line. If you can see your target, it means that there's nothing obstructing the path between you and your target. The only exception is if there's a transparent obstacle into the equation. Although you can see your target encased inside a glass cube, that glass counts as cover. You need a clear path to throw a rock at someone. If there's a wall but no ceiling between you and your target, nothing stops you from throwing the rock above the wall and have it land on your target, although it's easy to argue that this would be done with disadvantage. That's what a clear path is.
The only question that remains is whether or not your target benefits from total cover when using my mirror trick. The rules say that a target with total cover can't be targeted directly by an attack or a spell, but I don't think the target from my trick is actually benefiting from total cover. If it did, then that would mean throwing a rock above an obstacle and have it land on your target is impossible. That clearly makes no sense, so this is why my mirror trick should work. It could be argued that, depending on what the spell says, the target should have a bonus to its AC or Dexterity saving throw.
Age: 33 | Sex: Male | Languages: French and English | Roles: DM and Player
A mirror does not remove an obstruction between you and a target -- whether that target is a creature or a point in space for an AoE. It might let you see it, but that doesn't mean you can target it with a spell
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If you can see a target by using a mirror, it is no longer behind total cover.
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This is simply not true. If you can see a creature around the corner of a bending corridor 15 feet away from you, your arrow doesn't bend around the corner as you shoot, neither does it pass through the wall to hit your target.
But we're not talking about bows and arrows here. The fact that you can see your target via a mirror means that there's a clear path to it. Spells aren't bows and arrows. Unless it specifies that it requires a straight line, spells can bend and seek their target; some don't even have to because they aren't tangible, they just magically cause the target to suffer an effect. Are you actually going to tell me that there's no way for a thrown rock to lob over an obstacle and land on a target? Since when are straight lines an absolute necessity for everything? Heck, not even bows and arrows require a straight line. Arrows are affected by gravity. Real life archers aim for the sky when combating an army. They have to consider gravity and the wind, so they're always aiming above their target and adjusting their angle. Heck, the same actually applies with firearms. Snipers don't actually shoot in a straight line. Bullets are affected by gravity and the wind just like any other projectile. Are you going to tell me that because there are no straight line between the attacker and the target, it's impossible to hit it with any projectile?
Do you actually believe that a spell like charm person can only work if there's a straight line between the caster and the target? As long as your target is within range and you can see it, it works. Besides, half cover and three-quarters cover only affect spells that require a Dexterity saving throw, although some spells like sacred flame clearly specify that they ignore cover. Total cover is different, as it does prevent spells from directly targeting something. Sage Advice says that a spell such as charm person can be blocked by a glass window. But the RAW makes it clear: a target has total cover if it is completely concealed by an obstacle. In a scenario where your target is encased inside a glass cube, it is completely concealed by an obstacle. When I think about it more, what I previously said regarding sacred flame working in that scenario is wrong. It only says that the target gains no benefit from cover for their Dexterity saving throw, but total cover doesn't care. If you aren't allowed to target the thing inside that glass cube, it's simply not affected by the spell; no saving throw is required.
However, it becomes a different story if there's a hole in that glass cube. The latter suddenly becomes three-quarters cover because at least three-quarters of the target is covered and the target isn't completely concealed. In my mirror trick scenario, cover is relative. The caster has total cover from the target but the target doesn't have total cover from the caster. You can't say that the target is completely concealed because the caster can clearly see it and there's a clear path to it. As I explained before, a clear path doesn't have to be a straight line. You could draw a (non straight) line between the caster and the target. No barrier is preventing that line from reaching its target. In other words, the target doesn't benefit from total cover unless the spell specifies that it requires a straight line.
This at least works in theory. Someone needs to ask Sage Advice for clarification.
Age: 33 | Sex: Male | Languages: French and English | Roles: DM and Player
Using a mirror to look around corners might grant you vision of the target, not a clear path. It is effectively the same as if you use the Scrying spell to look at someone in another room: you don't suddenly have a clear path to the target just because you can see it. The walls between you still exist. If you are holding your mirror in your own space, it grants you no special benefits as your point of view is the same. If you hold it on a stick so it protrudes into an adjacent space, then there might be a clear path between the mirror and the target. However you are not your mirror. If you don't move into the same space as the mirror, you still wouldn't have a clear path to your target.
As you can see in the illustrations below, cover is measured from the attacker's space to the target's space.
Yes, the rules don't take gravity into account for targeting purposes.
Yes, the targeting rules requires a clear path between the attacker and the target. How you describe it narratively is another matter. If you want an example of how a specific rule that allows an attack that bends, take a look at the Arcane Archer's Seeking Arrow below. Again this is a specific rule, not how the game generally works.
No, as long as you have a clear path to the target it works. And if the target is situated behind total cover, you don't have a clear path to the target.
The spell description of Sacred Flame states that the target gains no benefit from cover for the spell's saving throw. What this means is that half cover would grant +2 to the dex save, three-quarters cover wouldn't grant +5 to the dex save, and full cover wouldn't prevent the caster from targeting the target. It doesn't mean the opposite. This is a specific rule, and specific rules beat general rules.
Again, being able to see someone and being able to target someone is not the same thing. Vision doesn't remove walls.
Thank you BeyondMisty for bringing some very good counterarguments to this debate.
Yeah, RAW sometimes make no sense. As a DM, I would still allow throwing a rock over an obstacle at disadvantage for 1d4 bludgeoning damage though. I would also rule throwing a non improvised weapon such as a javelin to only do 1d4 damage in this case, with the only difference being that it still adds the character's proficiency bonus to the attack roll. But in the case of a spell, I unfortunately really want to follow the RAW. Why? Because magic doesn't apply in real life, so I can't use real life logic.
Yes, that's basically what I meant, but thanks for putting it into other words to help other people understand it more.
Unless there's a spell that specifically bypasses the rules on total cover while still requiring seeing the target, I guess this really puts an end to my mirror trick. Does anyone know if such a spell even exist?
Age: 33 | Sex: Male | Languages: French and English | Roles: DM and Player
Being able to bypass total cover and requiring you to be able to see the target are mutually exclusive, so there couldn't be a spell that did that.
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