Obviously the opposite of cold damage is fire damage, opposite of piercing is probably force or bludgeoning, etc, but I can't find anything that's a good opposite for radiant damage. For context, I'm running a campaign set in Hell. One of my players is a paladin, which is all good, but they do radiant damage...which hurts demons a fair bit, so I'm planning on changing it. I'm just not exactly sure what to. I was thinking of necrotic, but I always envisioned that as a rot and decay type of damage, rather than a burst like radiant is. Maybe I'm overthinking this. Anyways, opinions would be much appreciated!!
Edit because people have commented on it (this isn't meant to be rude, ya girl just wanted to clear it up): My paladin player is totally on board with changing the damage types and enemies damaged by their abilities; we both wanted to figure out the opposites of each. They're also completely allowed to play a paladin.
Generally but not in all cases, Radiant damage is from some sort of holy or divine source. So Necrotic would be a decent bet for something corrupt or dark. Creatures like Shadow deal Necrotic damage (the opposite of light).
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"Sooner or later, your Players are going to smash your railroad into a sandbox."
-Vedexent
"real life is a super high CR."
-OboeLauren
"............anybody got any potatoes? We could drop a potato in each hole an' see which ones get viciously mauled by horrible monsters?"
To bolster Wyspera, you'll notice certain types of magical abilities will have the character choose either radiant or necrotic (or at least one, where I thought "cool, cooler if it'd require commitment) ... so I think the designers saw them as a duality. My head cannon has radiant, while wielded by divine entities, actually comes from positive plane, necrotic the negative plane, those to planes in the default cosmology in 5e actually envelope the whole cosmology.
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Jander Sunstar is the thinking person's Drizzt, fight me.
The way damage types seem to work is that they are categorized. They don't have an intrinsic duality to them. You're imposing your own feelings on the elements, and that's okay. That also means that you can pick whatever you like.
Example: Radiant's foil could be Psychic. Radiant is holy, and good, based in the soul(1) and feelings(2). Psychic on the other hand is mental(2) and logical(1). As in Psychic energy comes from your ego, while radiant comes from the super-ego.
Or else you could do the common Radiant v. Necrotic as Radiant and healing spells came from the Positive energy plane, while Necrotic and sickness spells came from the Negative energy plane.
If you're curious, those actual categories are Non-Magical (bludgeoning, piercing, slashing), Natural / Elemental (Acid, Cold, Fire, Lightning, Poison, Thunder), and the super natural (Force, Necrotic, Psychic, Radiant).
spirit guardians: “On a failed save, the creature takes 3d8 radiant damage (if you are good or neutral) or 3d8 necrotic damage (if you are evil).”
barbarian path of the zealot: “The extra damage is necrotic or radiant; you choose the type of damage when you gain this feature.”
protector Aasimar versus fallen Aasimar:
protector - “Starting at 3rd level, you can use your action to unleash the divine energy within yourself… you can deal extra radiant damage to one target”
fallen - “Starting at 3rd level, you can use your action to unleash the divine energy within yourself… you can deal extra necrotic damage“
they are only some examples, your game - play it how you like.
"Radiation" is something that most people don't really understand all that well. They have a vague idea that it turns people into Mutants and that it's colored Green. In actual fact, about the only kind of radiation that is visible at all glows blue. If you see something radioactive that is glowing blue, you are probably dead and just don't know it yet. The nearest thing you can get to describing what radiation really does is that it gives you an internal sunburn. It destroys cells from the inside. That's sort of how Microwave ovens work, and why they used to cook from the inside out in the really old models.
Radiation scares people. There was a huge panic some years ago when a huge earthquake damaged a nuclear reactor in Japan and the wave of radiation supposedly was strong enough to make it all the way to the US. It did, more or less, but the guy who does the XKDC comic strip made a little chart to show just how much radiation it was that reached the coast, and it turns out to be less than you get when they take an X-ray of you. Old style cathode ray tube color televisions used to emit more radiation than that.
Radiant damage has in effect become Holy, and if you read the descriptions of what it does, it burns things. It's Holy Fire, and it cleanses the Unclean. It does extra damage to creatures of the Lower planes and to the Undead. The opposite (in the sense that there are opposites, since not all things have such) is Necrotic damage. Necrosis is the process of decay and cases things to rot. It's really more the opposite of healing, but the energy that causes things to heal isn't really defined. It's the energy of Life, part of the force of Nature, it rebuilds and regenerates the cells. Another thing that is associated with Death is the "chill of the grave". Dead things cool off, so the opposite of Holy Fire might be considered Death's Chill or Cold damage.
Another odd thought. In ancient times, the most important test to see if someone was still alive was to see if they were breathing. The Latin word for breathing is Spiros, and when you die, you Expire, which means you breathe out your last breath. Breathing life into something is to Inspire. Spirits were a sort of separate thing from living beings, and they animated things kind of like a soul does. D&D retains that in a way, things that are considered "spirits" return to their home plane once their shell is destroyed, so Elves go back to the Feywild to be re-incarnated, Demons go back to the Abyss, Devils go back to Hell and so on. The most mighty of all Spirits are the gods. Souls go right back to the gods who created them rather than going back to a home plane. As near as I can figure, Spirits are what animate things that have the odd sort of immortality that lasts until something kills the shell of whatever hold the spirit. Souls exist because spirits cannot reproduce themselves. The only way to get more Demons is to turn a soul into one. That's why Demons and Devils are so interested as to be willing to bargain with mortals. They want more souls.
So in terms of the natural elements, souls and spirits are made of Air, so Fire burns them, but Earth really doesn't do much to them, Water is a healing force, and there is a Fifth Element, or Quintessence that is often called Mana and is the energy that powers spells.
Cold puts out fires. Acid is sometimes described as burning things, but what it actually does is destroy everything, not just cells by breaking molecular bonds. It eats things. Lightning also burns things and has a nasty habit if hitting the nerves rather than the other cells. That's what Electricity really does. It's ultra high temperature plasma that burns and channels along metals as well as harming the nerves because they conduct electricity in a small way. Thunder is Sonic damage, which is really a sort of Bludgeoning spread out over such a large area that it only damages things that are very delicate. Psychic damage works directly on the mind. In D&D, force damage directly reduces hit points until they are gone and then does bludgeoning damage to the body itself.
Poison is hard to explain in D&D. some types damage the cells and do damage. Others just make you tired. They take away the energy you need to move around and stay awake. Disease attacks the cells and produces poisons as a byproduct. Most diseases are microscopic living creatures, but Viruses change the cells themselves to make them produce more Viruses. They reprogram the genetic code that is the blueprint that makes more cells. Some do this permanently. They are called "retro-viruses."
They still don't know what causes Cancer, but it works in a similar way. The cells become changed and go wild, making more and more instead of stopping once things have been repaired. Organs infested with Cancer fail after a while and when it doesn't attack the organs, it creates enough of itself to squeeze the organs enough that they stop working.
Oddly enough, while it can't be cured, some forms of Cancer can be reduced or even killed by Radiation.
So there you go. I'm off to have some of the water of life, take a breather, and get some rest. I need to regenerate my mana or I won't be able to cast spells. I could use a Long Rest.
"Radiation" is something that most people don't really understand all that well. They have a vague idea that it turns people into Mutants and that it's colored Green. In actual fact, about the only kind of radiation that is visible at all glows blue. If you see something radioactive that is glowing blue, you are probably dead and just don't know it yet. The nearest thing you can get to describing what radiation really does is that it gives you an internal sunburn. It destroys cells from the inside. That's sort of how Microwave ovens work, and why they used to cook from the inside out in the really old models.
I do not want more misinformation to spread that it already has, but electromagnetic raditation is not limited by color. Electromagnetic radation includes everything from radiowaves to gamma rays, and that includes the visible light spectrum as well. If you can see something with your eyes, you are seeing the radiation the thing gives off, whether it is red, blue, green, white, or anything in between. And hazardous radioactivity is not limited to the color blue either; sunlight is white and you can die overtime from overexposure to its high energy radiation even under the protection of earth's atmosphere which blocks most of it (assuming you did not die from the heat first). Microwaves (the appliance) uses microwaves to vibrate water molecules, heating them up in the process. High energy radiation like gamma rays damage cells by removing electrons in an atom, and ionized atoms interact differently from their non ionized versions, which can cause problems.
One of my players is a paladin, which is all good, but they do radiant damage...which hurts demons a fair bit, so I'm planning on changing it.
You didn't ask, but I would recommend against this for two reasons:
You control literally every aspect of the world except the PCs. You should not meddle in their abilities. You could have some demons be resistant to radiant, you could add HP to all demons, you could increase their defenses, you could make radiant damage power them up somehow, you could add more demons, give them non-demon allies, the options go on and on. Change things on your side, not on the PC side.
Paladins are supposed to be good at smiting demons and such. It's a part of the class identity. Shutting that down because it's inconvenient for you just feels unfair. What is the point of players making smart/effective decisions if you nullify decisions that are too smart? It just sets up a bad dynamic between you and your players. Let PCs be good at the stuff they're supposed to be good at.
If you're worried about challenge, maybe add more encounters where the goal is something other than just destroying all demons. Save the prisoner, disrupt the ritual, etc.
Yeah, the opposite of Radiant damage is Necrotic damage, almost all the time. Radiant damage is the damage of light/radiance (including radioactivity), while Necrotic damage is the damage type of darkness, shown by creatures such as the shadow, nightwalker, and most undead/shadow-creatures. Radiance is typically connected to life, as plants can't survive without light and humans are blind without light, but too much light (i.e. effects that deal radiant damage and/or blind) can be harmful. Necrotic damage is the damage type connected with decomposition, darkness, and withering, and thus connected with death.
In previous editions there were even "Positive" and "Negative" energy types (which were their equivalents to necrotic and radiant damage). Positive Energy would heal living creatures and harm undead, while Negative Energy would heal undead and harm living creatures (you can still see remnants of this in the negative energy flood spell, which heals undead and can turn creatures that it kills into zombies).
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Please check out my homebrew, I would appreciate feedback:
One of my players is a paladin, which is all good, but they do radiant damage...which hurts demons a fair bit, so I'm planning on changing it.
You didn't ask, but I would recommend against this for two reasons:
You control literally every aspect of the world except the PCs. You should not meddle in their abilities. You could have some demons be resistant to radiant, you could add HP to all demons, you could increase their defenses, you could make radiant damage power them up somehow, you could add more demons, give them non-demon allies, the options go on and on. Change things on your side, not on the PC side.
Paladins are supposed to be good at smiting demons and such. It's a part of the class identity. Shutting that down because it's inconvenient for you just feels unfair. What is the point of players making smart/effective decisions if you nullify decisions that are too smart? It just sets up a bad dynamic between you and your players. Let PCs be good at the stuff they're supposed to be good at.
If you're worried about challenge, maybe add more encounters where the goal is something other than just destroying all demons. Save the prisoner, disrupt the ritual, etc.
It's also good to remember that not everything that lives in the Lower Planes is a fiend. And Divine Smite only adds an extra 1d8 damage vs Fiends. That only averages 4.5 more damage per smite.
Rollback Post to RevisionRollBack
Find your own truth, choose your enemies carefully, and never deal with a dragon.
"Canon" is what's factual to D&D lore. "Cannon" is what you're going to be shot with if you keep getting the word wrong.
One of my players is a paladin, which is all good, but they do radiant damage...which hurts demons a fair bit, so I'm planning on changing it.
You didn't ask, but I would recommend against this for two reasons:
You control literally every aspect of the world except the PCs. You should not meddle in their abilities. You could have some demons be resistant to radiant, you could add HP to all demons, you could increase their defenses, you could make radiant damage power them up somehow, you could add more demons, give them non-demon allies, the options go on and on. Change things on your side, not on the PC side.
Paladins are supposed to be good at smiting demons and such. It's a part of the class identity. Shutting that down because it's inconvenient for you just feels unfair. What is the point of players making smart/effective decisions if you nullify decisions that are too smart? It just sets up a bad dynamic between you and your players. Let PCs be good at the stuff they're supposed to be good at.
If you're worried about challenge, maybe add more encounters where the goal is something other than just destroying all demons. Save the prisoner, disrupt the ritual, etc.
Also there's resource consumption involved. For a paladin to do radiant damage they generally need to cast a spell or use a spell slot on a smite. (They eventually get improved divine smite but that's like what, level 11?)
Also there's resource consumption involved. For a paladin to do radiant damage they generally need to cast a spell or use a spell slot on a smite. (They eventually get improved divine smite but that's like what, level 11?)
And even then, the damage bump against fiends doesn't apply to Improved Divine Smite, so I wouldn't worry about it either.
That said, Since the OP's edit clarifies the player involved is on board, I'd say Necrotic damage is probably the best bet here.
I would point out that every fiend in the monster manual takes identical damage from radiant and necrotic (none are vulnerable, resistant, or immune to either one). Radiant is generally more useful than necrotic because many undead suffer some type of increased effect from radiant and/or have resistance to necrotic, and almost nothing is resistant to radiant, but in campaign set in Hell it won't make much difference.
I believe the lasers in Icewind Dale do radiant damage, as does the dragon construct…. So radiant isn’t -always- divine damage.
Not always, but it often is. Light is connected to the sky/"heavens", because stars (including the Sun) make light. The "heavens" were often connected with our gods (whether that be the Judeo-Islamic-Christian capital-g God, or the gods from the Greco-Roman pantheon, Norse Mythology, or any of the others), and these were in-turn connected to Celestials in D&D, so Celestials are often connected with light (thus radiant damage) and the opposite of Celestials (which are Fiends and Undead) get other damage types (often fire for Fiends, and Necrotic for Undead).
It's not always divine, but it is more often than not. Yes, Laser Pistols, Laser Rifles, Circle of Stars Druids, and Sickening Radiance do Radiant damage and aren't strictly "holy/divine" (although an army of Aasimar/Archons that use Laser Weapons would be awesome), most sources of radiant damage in the game are divine.
Would I like to see more sources of non-holy radiant damage in D&D? Yes. However, that doesn't change the fact that there is a strong tie between radiance and divinity in D&D.
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Please check out my homebrew, I would appreciate feedback:
Obviously the opposite of cold damage is fire damage, opposite of piercing is probably force or bludgeoning, etc, but I can't find anything that's a good opposite for radiant damage. For context, I'm running a campaign set in Hell. One of my players is a paladin, which is all good, but they do radiant damage...which hurts demons a fair bit, so I'm planning on changing it. I'm just not exactly sure what to. I was thinking of necrotic, but I always envisioned that as a rot and decay type of damage, rather than a burst like radiant is. Maybe I'm overthinking this. Anyways, opinions would be much appreciated!!
Edit because people have commented on it (this isn't meant to be rude, ya girl just wanted to clear it up): My paladin player is totally on board with changing the damage types and enemies damaged by their abilities; we both wanted to figure out the opposites of each. They're also completely allowed to play a paladin.
Generally but not in all cases, Radiant damage is from some sort of holy or divine source. So Necrotic would be a decent bet for something corrupt or dark. Creatures like Shadow deal Necrotic damage (the opposite of light).
"Sooner or later, your Players are going to smash your railroad into a sandbox."
-Vedexent
"real life is a super high CR."
-OboeLauren
"............anybody got any potatoes? We could drop a potato in each hole an' see which ones get viciously mauled by horrible monsters?"
-Ilyara Thundertale
To bolster Wyspera, you'll notice certain types of magical abilities will have the character choose either radiant or necrotic (or at least one, where I thought "cool, cooler if it'd require commitment) ... so I think the designers saw them as a duality. My head cannon has radiant, while wielded by divine entities, actually comes from positive plane, necrotic the negative plane, those to planes in the default cosmology in 5e actually envelope the whole cosmology.
Jander Sunstar is the thinking person's Drizzt, fight me.
The way damage types seem to work is that they are categorized. They don't have an intrinsic duality to them. You're imposing your own feelings on the elements, and that's okay. That also means that you can pick whatever you like.
Example: Radiant's foil could be Psychic. Radiant is holy, and good, based in the soul(1) and feelings(2). Psychic on the other hand is mental(2) and logical(1). As in Psychic energy comes from your ego, while radiant comes from the super-ego.
Or else you could do the common Radiant v. Necrotic as Radiant and healing spells came from the Positive energy plane, while Necrotic and sickness spells came from the Negative energy plane.
If you're curious, those actual categories are Non-Magical (bludgeoning, piercing, slashing), Natural / Elemental (Acid, Cold, Fire, Lightning, Poison, Thunder), and the super natural (Force, Necrotic, Psychic, Radiant).
Necrotic
Some examples;
spirit guardians: “On a failed save, the creature takes 3d8 radiant damage (if you are good or neutral) or 3d8 necrotic damage (if you are evil).”
barbarian path of the zealot: “The extra damage is necrotic or radiant; you choose the type of damage when you gain this feature.”
protector Aasimar versus fallen Aasimar:
protector - “Starting at 3rd level, you can use your action to unleash the divine energy within yourself… you can deal extra radiant damage to one target”
fallen - “Starting at 3rd level, you can use your action to unleash the divine energy within yourself… you can deal extra necrotic damage“
they are only some examples, your game - play it how you like.
"Radiation" is something that most people don't really understand all that well. They have a vague idea that it turns people into Mutants and that it's colored Green. In actual fact, about the only kind of radiation that is visible at all glows blue. If you see something radioactive that is glowing blue, you are probably dead and just don't know it yet. The nearest thing you can get to describing what radiation really does is that it gives you an internal sunburn. It destroys cells from the inside. That's sort of how Microwave ovens work, and why they used to cook from the inside out in the really old models.
Radiation scares people. There was a huge panic some years ago when a huge earthquake damaged a nuclear reactor in Japan and the wave of radiation supposedly was strong enough to make it all the way to the US. It did, more or less, but the guy who does the XKDC comic strip made a little chart to show just how much radiation it was that reached the coast, and it turns out to be less than you get when they take an X-ray of you. Old style cathode ray tube color televisions used to emit more radiation than that.
Radiant damage has in effect become Holy, and if you read the descriptions of what it does, it burns things. It's Holy Fire, and it cleanses the Unclean. It does extra damage to creatures of the Lower planes and to the Undead. The opposite (in the sense that there are opposites, since not all things have such) is Necrotic damage. Necrosis is the process of decay and cases things to rot. It's really more the opposite of healing, but the energy that causes things to heal isn't really defined. It's the energy of Life, part of the force of Nature, it rebuilds and regenerates the cells. Another thing that is associated with Death is the "chill of the grave". Dead things cool off, so the opposite of Holy Fire might be considered Death's Chill or Cold damage.
Another odd thought. In ancient times, the most important test to see if someone was still alive was to see if they were breathing. The Latin word for breathing is Spiros, and when you die, you Expire, which means you breathe out your last breath. Breathing life into something is to Inspire. Spirits were a sort of separate thing from living beings, and they animated things kind of like a soul does. D&D retains that in a way, things that are considered "spirits" return to their home plane once their shell is destroyed, so Elves go back to the Feywild to be re-incarnated, Demons go back to the Abyss, Devils go back to Hell and so on. The most mighty of all Spirits are the gods. Souls go right back to the gods who created them rather than going back to a home plane. As near as I can figure, Spirits are what animate things that have the odd sort of immortality that lasts until something kills the shell of whatever hold the spirit. Souls exist because spirits cannot reproduce themselves. The only way to get more Demons is to turn a soul into one. That's why Demons and Devils are so interested as to be willing to bargain with mortals. They want more souls.
So in terms of the natural elements, souls and spirits are made of Air, so Fire burns them, but Earth really doesn't do much to them, Water is a healing force, and there is a Fifth Element, or Quintessence that is often called Mana and is the energy that powers spells.
Cold puts out fires. Acid is sometimes described as burning things, but what it actually does is destroy everything, not just cells by breaking molecular bonds. It eats things. Lightning also burns things and has a nasty habit if hitting the nerves rather than the other cells. That's what Electricity really does. It's ultra high temperature plasma that burns and channels along metals as well as harming the nerves because they conduct electricity in a small way. Thunder is Sonic damage, which is really a sort of Bludgeoning spread out over such a large area that it only damages things that are very delicate. Psychic damage works directly on the mind. In D&D, force damage directly reduces hit points until they are gone and then does bludgeoning damage to the body itself.
Poison is hard to explain in D&D. some types damage the cells and do damage. Others just make you tired. They take away the energy you need to move around and stay awake. Disease attacks the cells and produces poisons as a byproduct. Most diseases are microscopic living creatures, but Viruses change the cells themselves to make them produce more Viruses. They reprogram the genetic code that is the blueprint that makes more cells. Some do this permanently. They are called "retro-viruses."
They still don't know what causes Cancer, but it works in a similar way. The cells become changed and go wild, making more and more instead of stopping once things have been repaired. Organs infested with Cancer fail after a while and when it doesn't attack the organs, it creates enough of itself to squeeze the organs enough that they stop working.
Oddly enough, while it can't be cured, some forms of Cancer can be reduced or even killed by Radiation.
So there you go. I'm off to have some of the water of life, take a breather, and get some rest. I need to regenerate my mana or I won't be able to cast spells. I could use a Long Rest.
<Insert clever signature here>
I do not want more misinformation to spread that it already has, but electromagnetic raditation is not limited by color. Electromagnetic radation includes everything from radiowaves to gamma rays, and that includes the visible light spectrum as well. If you can see something with your eyes, you are seeing the radiation the thing gives off, whether it is red, blue, green, white, or anything in between. And hazardous radioactivity is not limited to the color blue either; sunlight is white and you can die overtime from overexposure to its high energy radiation even under the protection of earth's atmosphere which blocks most of it (assuming you did not die from the heat first). Microwaves (the appliance) uses microwaves to vibrate water molecules, heating them up in the process. High energy radiation like gamma rays damage cells by removing electrons in an atom, and ionized atoms interact differently from their non ionized versions, which can cause problems.
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My understanding of the damage opposites/foils:
Necrotic (unholy shadows) / Radiant (divine light)
Force (Ethereal) / Psychic (Astral)
Bludgeoning / Slashing / Piercing
Fire / Cold
Lightning / Thunder
Acid / Poison
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Spells, Monsters, Magic Items, Feats, Subclasses.
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Extended Signature
You didn't ask, but I would recommend against this for two reasons:
If you're worried about challenge, maybe add more encounters where the goal is something other than just destroying all demons. Save the prisoner, disrupt the ritual, etc.
My homebrew subclasses (full list here)
(Artificer) Swordmage | Glasswright | (Barbarian) Path of the Savage Embrace
(Bard) College of Dance | (Fighter) Warlord | Cannoneer
(Monk) Way of the Elements | (Ranger) Blade Dancer
(Rogue) DaggerMaster | Inquisitor | (Sorcerer) Riftwalker | Spellfist
(Warlock) The Swarm
Yeah, the opposite of Radiant damage is Necrotic damage, almost all the time. Radiant damage is the damage of light/radiance (including radioactivity), while Necrotic damage is the damage type of darkness, shown by creatures such as the shadow, nightwalker, and most undead/shadow-creatures. Radiance is typically connected to life, as plants can't survive without light and humans are blind without light, but too much light (i.e. effects that deal radiant damage and/or blind) can be harmful. Necrotic damage is the damage type connected with decomposition, darkness, and withering, and thus connected with death.
In previous editions there were even "Positive" and "Negative" energy types (which were their equivalents to necrotic and radiant damage). Positive Energy would heal living creatures and harm undead, while Negative Energy would heal undead and harm living creatures (you can still see remnants of this in the negative energy flood spell, which heals undead and can turn creatures that it kills into zombies).
Please check out my homebrew, I would appreciate feedback:
Spells, Monsters, Subclasses, Races, Arcknight Class, Occultist Class, World, Enigmatic Esoterica forms
It's also good to remember that not everything that lives in the Lower Planes is a fiend. And Divine Smite only adds an extra 1d8 damage vs Fiends. That only averages 4.5 more damage per smite.
Find your own truth, choose your enemies carefully, and never deal with a dragon.
"Canon" is what's factual to D&D lore. "Cannon" is what you're going to be shot with if you keep getting the word wrong.
Also there's resource consumption involved. For a paladin to do radiant damage they generally need to cast a spell or use a spell slot on a smite. (They eventually get improved divine smite but that's like what, level 11?)
And even then, the damage bump against fiends doesn't apply to Improved Divine Smite, so I wouldn't worry about it either.
That said, Since the OP's edit clarifies the player involved is on board, I'd say Necrotic damage is probably the best bet here.
I would point out that every fiend in the monster manual takes identical damage from radiant and necrotic (none are vulnerable, resistant, or immune to either one). Radiant is generally more useful than necrotic because many undead suffer some type of increased effect from radiant and/or have resistance to necrotic, and almost nothing is resistant to radiant, but in campaign set in Hell it won't make much difference.
I believe the lasers in Icewind Dale do radiant damage, as does the dragon construct…. So radiant isn’t -always- divine damage.
The lasers in the DMG do radiant -- laser pistol and laser rifle. And it's really hard to view Sickening Radiance as divine...
Not always, but it often is. Light is connected to the sky/"heavens", because stars (including the Sun) make light. The "heavens" were often connected with our gods (whether that be the Judeo-Islamic-Christian capital-g God, or the gods from the Greco-Roman pantheon, Norse Mythology, or any of the others), and these were in-turn connected to Celestials in D&D, so Celestials are often connected with light (thus radiant damage) and the opposite of Celestials (which are Fiends and Undead) get other damage types (often fire for Fiends, and Necrotic for Undead).
It's not always divine, but it is more often than not. Yes, Laser Pistols, Laser Rifles, Circle of Stars Druids, and Sickening Radiance do Radiant damage and aren't strictly "holy/divine" (although an army of Aasimar/Archons that use Laser Weapons would be awesome), most sources of radiant damage in the game are divine.
Would I like to see more sources of non-holy radiant damage in D&D? Yes. However, that doesn't change the fact that there is a strong tie between radiance and divinity in D&D.
Please check out my homebrew, I would appreciate feedback:
Spells, Monsters, Subclasses, Races, Arcknight Class, Occultist Class, World, Enigmatic Esoterica forms
Radiant damage is decently available to non-divine spellcasters starting with 4th level spells -- Sickening Radiance, Wall of Light, Sunbeam, Crown of Stars, and Sunburst -- but high level spells don't have the visibility of options like Sacred Flame, Guiding Bolt, and Spirit Guardians.