i think we all know what the exhaustion condition does but just so that we are all on the same page:

exhaustion is measured in six levels, and an effect can give an creature one or more levels, as specified in that effects description. Having one level of exhaustion leads to an target having disadvantage on all abillity checks, level two is level one plus your speed is halved, level three is like level two but you also gain disadvantage on all attack rolls and saving throws, so on and so fourth with the effects getting more and more severe until finally, if you reach six levels of exhaustion you instantly die

long rests can remove one level of exhaustion, and some spells remove one level of exhaustion, or all of them at once.

And along comes sickening radiance, an spell from xanatars guide to everything. It affects all creatures within an 30ft radius centered around a point within range, and all creatures who enter the area for the first time on their turn or start their turn there must make an constitution saving throw or take 4d10 radiant damage, suffer one level of exhaustion and start to glow.

now i may have misinterpreted this spell, but if i read this correctly, that means that every time you fail this save, you gain one level of exhaustion. An spell caster can theoretically concentrate on this spell for up to 10 minutes, or 100 rounds of combat, so that means that if an spell caster manages to trap an victim in the area of one of these spells, and the spellcaster concentrates on the spell for the full duration, the target must make one hundred constitution saving throws, and as long as the victim is not immune to exhaustion like many undead, they are guaranteed to die as long as they fail only six of those hundred constitution saving throws.

and for the creatures who ARE immune to exhaustion, you can simply have a fellow spellcaster cast polymorph on that target. Since the target will not retain its condition immunities oppon getting transformed, and since creatures who revert as a result of death and not hit point loss seem to remain dead once they revert according to some official rulings (i think)

maybe i missunderstood the spell, and only a single level of exhaustion can be granted by this spell per creature affected by this spell, i dont know, maybe i am wrong, and maybe this is fine since if used in most combat encounters the enemy could not only escape, but your allies could potentially be harmed by it, but i really dont know shit, despite knowing a lot about the rules and owning a lot of the sourcebooks, i have had kinda limited practical experiencnce, and i have never played a character above level three, maybe this is the sort of things people are doing at 7th level, how am i supposed to know? But this really feels out of place, this spell feels to powerful for its level

You didn't misunderstand it, the exhaustion levels do accumulate.
But I do not see it as overpowered in any way... especially seeing as to how it is a 4th level spell, requires the caster to maintain concentration for all those rounds, and most likely requires an ability of an additional character to immobilize the creature in that area.

We're talking 6 full rounds of concentration failures to die from exhaustion. I rarely have seen any round of combat go that long.

I've seen the cantrip thorn whip pull people into bottomless pits before....
... it's all in fun and games I suppose.

It’s not overpowered because it’sa combat spell. Combats rarely go that long. I can’t remember the last thing in combat that an enemy stayed in an AOE spell of ANY kind for more than 3 rounds without dying or escaping.

Note that sickening radiance does not prevent the enemy from leaving at all, so they can just walk out of the area! So to restrain them you need a second spell caster. And they have to fail THAT save too. 

So yeah, a creature that is under the continuous effect of two spells for more than 6 rounds is gonna die. That’s honestly on the slow side, typically in combat enemies should be killed way faster than that.

I agree with your interpretation of how the spell works but I don’t think that it’s overpowered in the slightest. 

1. When you make your save you don’t suffer from any effect. Compare that to other spells where when you make your save you take half damage.
2. The Spell is visible so it’s easy to avoid going into its area when you’re not already in its area. 
3. There isn’t anything holding you in the area of the spell so it’s easy to move out of the area of the spell. 

I think that it’s a great spell when you’re working with a team mate who can either move opponents into its area of effect or immobilize opponents who are in its area of effect, but without that teamwork it’s nothing special. With that teamwork it’s devastating!

counterpoint: passwall, wall of stone, magic circle, levitate, stone shape, gust of wind, fear, all of these could if put in the right context be used to in some way trap an target. heck there is no need, just buy an ******* nonmagical human sized cage and trap the bbeg in it. And the thing is the ultimate guillotine like "fairness" or "democracy" of it all. It does not matter if you are the poor goblin soul put on cage duty or the big bad with hundreds of hit points, both are ultimately doomed in the face of this trap, it does not matter how many hit points you have, how high your armor class is, how many damage resistances and immunities you have, how many hit points you can restore in a single round, no matter that you have three daily uses of legendary resistances, if you happen to not be immune to this specific condition and you have no means of escaping the trap the players made within 10 minutes, and your bonus to con saves happens to be three points lower than the casters spell save DC, you are dead, doomed to wither away, dying an antagonizingly slow death as you cough up your innards and you finally succumb to that foul green light

yeah but if you cast this mid combat it is kinda trash since an victim can just ******* walk out. Yeah i did notice how it does not do half damage on a failed save unlike fireball and the like, but does it matter if i have chained my victim to the wall in an locked jail cell and is only using this spell as an execution tool? does the damage really matter if the target only needs to fail six times out of one hundred for them to die? does the average damage really matter in that case?

and yes, most of the spells i mentioned need concentration, but that issue can be resolved with an casting of glyph of warding. Yes there are many monsters immune to exhaustion, most notably stronger monsters and undead, but many are not, and most monsters who are not can be turned into monsters who are with polymorph, as long as you make shure to heal the created polymorphed creature so that it does not get reduced to zero hit points, i just feel that in combination with other game effects, this spell could be rather potent and deadly, that even an lone wizard could with enough prepreation and a bit of luck use this spell to slay monsters far more powerful than he, i feel that this spell could be just an very potent spell.

maybe i am overreacting, but i just think this spell is really cool

Forcecage + Sickening Radiance is a brutal combo. But, Dispel Magic, Counterspell, Antimagic Field, Beholders, Astral Dreadnaughts, Disintegrate, Teleportation, and spaces too small for the AoE without capturing yourself, and the usefulness of either spell and especially the combo go way down.

Also, the DM is the D&D God of Gods, abuse the spell and suddenly you'll find yourself in too many situations where it cannot be used or they'll just let you use it over and over, but decrease rewards/experience considerably - your eventual impatience at getting rich and boredom of doing the same routine every time without risk, will most assuredly curb your exploitive spellcasting habits in no time at all.

If you have trapped the BBEG in a cage or chained them to a wall with no way for them to escape, you have already won. At that point, sickening radiance would just be using a spell slot to do a little faster what cantrips could do for free.

By the time you start using polymorph to kill creatures with immunity to exhaustion, you are talking about 2 or 3 spellcasters burning 10 spell slots (to heal the bad guy) plus an extra one for every legendary resistance. And polymorph is already a powerful, combat ending spell in its own right, this is just adding extra steps and resources.

Sickening radiance is definitely a powerful spell with powerful combos, but it is not overpowered. By the time they die from exhaustion, they will have already taken 132 (24d10) damage which will kill most monsters under CR8 anyway.

Sickening Radiance does probably outperform Cloudkill, despite being a lower level spell (bigger area, more controllable, better damage type, about the same damage, extra condition which has a kill effect). But it has a (slightly) more selective list of classes to which its available, so maybe that's ok? 

Might be a little overtuned (I think 3d8 or even 3d6 would have been more appropriate than 4d10), but the "kill a boss with impunity" setups for the spell are niche enough to where they aren't really cause for concern. 

how do you insert tool tips like Sickening Radiance ? i really need to know. also it just feels wrong to know that with just six failed saves, any creature could die at the hands of this spell, something made easier if we have an warlock with those weird push/pull eldritch invocation effects or some other character with good push power

Quote from DxJxC >>

If you have trapped the BBEG in a cage or chained them to a wall with no way for them to escape, you have already won. At that point, sickening radiance would just be using a spell slot to do a little faster what cantrips could do for free.

By the time you start using polymorph to kill creatures with immunity to exhaustion, you are talking about 2 or 3 spellcasters burning 10 spell slots (to heal the bad guy) plus an extra one for every legendary resistance. And polymorph is already a powerful, combat ending spell in its own right, this is just adding extra steps and resources.

Sickening radiance is definitely a powerful spell with powerful combos, but it is not overpowered. By the time they die from exhaustion, they will have already taken 132 (24d10) damage which will kill most monsters under CR8 anyway.

 trapped does not nessesarily mean defenseless, it is not certain you can kill somebody in less than 10 minutes, but this spell could. Also watching them cough up their own blood as they slowly die of radiation poisoning is way cooler (and for the villain, way more dignified) than death by a thousand fire bolts

[ spell ]Sickening Radiance[ /spell ]
(without the spaces though)

Full list is here

Quote from Chicken_Champ >>

Sickening Radiance does probably outperform Cloudkill, despite being a lower level spell (bigger area, more controllable, better damage type, about the same damage, extra condition which has a kill effect). But it has a (slightly) more selective list of classes to which its available, so maybe that's ok? 

Might be a little overtuned (I think 3d8 or even 3d6 would have been more appropriate than 4d10), but the "kill a boss with impunity" setups for the spell are niche enough to where they aren't really cause for concern. 

 Cloudkill fully out performs sickening radiance in terms of damage amount. It only does 2.5 more average damage on a failed save, but it does 11.25 more average damage on successful save. No argument for everything else you said though (especially damage type).

Quote from ArtificeMeal >>

 trapped does not nessesarily mean defenseless, it is not certain you can kill somebody in less than 10 minutes, but this spell could. Also watching them cough up their own blood as they slowly die of radiation poisoning is way cooler (and for the villain, way more dignified) than death by a thousand fire bolts

 A level 7 cleric could kill a tarasque with cantrips in 10 minutes if it was restrained that long.

If the enemy has high CON it could still take quite a while, and like I said creatures under CR 8 would be killed by the damage (therefore any equivalent damage) before the exhaustion. Plus over 260 monsters are immune to exhaustion (~16%).

And I don't think a villain would consider being whittled to a weak, sickly shell of their former self is dignified.

Quote from DxJxC >>

[...] A level 7 cleric could kill a tarasque with cantrips in 10 minutes if it was restrained that long.

If the enemy has high CON it could still take quite a while, and like I said creatures under CR 8 would be killed by the damage (therefore any equivalent damage) before the exhaustion. Plus over 260 monsters are immune to exhaustion (~16%).

And I don't think a villain would consider being whittled to a weak, sickly shell of their former self is dignified.

 you absolutely shure an level 7 cleric could defeat the tarrasque with cantrips in ten minutes? The tarrasque, with its magic resistance and 676 hit points? Well it might work if the tarrasque is restrained or otherwise has disadantage on dex saves the entire duration and you only use sacred flame as your only attack. Becuase without such benefits, the tarrasque will always have advantage on all saving throws against spells. Now i did the math myself, since an level 7 cleric is expected to have an wisdom score of 18 and an proficiency bonus of +3, an level 7 cleric should have an spell save DC of 15, that means that when the tarrasque makes its saving throw, it will suceed on a roll of 15, 16, 17, 18, 19 or 20, or an 6/20 chance of succeeding on an saving throw, or an 30% chance, but since the tarrasque has advantage on the saving throw (magic resistance), that means that there is only an 196/400 chance of the tarrasque failing an saving throw against the sacred flame cantrip, or an 49% chance of an failed save. At 7th level, the sacred flame cantrip deals 2d8 damage, or 9 damage on average, and if we multiply the chance for an cleric to hit (0.49), with the number of times sacred flame is cast (100), with the average damage per hit (9) we get that on average an cleric could deal on average 441 damage to an tarrasque in 100 rounds of combat.

Now of course, this example is really bad becuase an tarrasque has so good con that it would on average (assuming no usage of legendary resistance) Pass the save an average of four times, way less than the six failed saves needed to kill an tarrasque, and i get that you were probably using the term "A level 7 cleric could kill a tarasque with cantrips in 10 minutes if it was restrained that long." as an hyperbole, meaning that all this math i did was completely useless in defending my point but eh

and as for why i think sickening radiance is more dignified, well because with sickening radiance you can take the villains death seriously, wheras if you chain him or her to the wall and cast fire bolt on them on repeat for then minutes, well it would look ridiculous, the villain, and by extension all that that villain acomplished, would be reduced to an punchline. This spell is quieter, more subtile, and quite useful. And also, anyone could just push somebody into a small room, cast this spell within it, close the door and lock the room and boom, instant death trap that best of all leaves no traces of bodily harm, which will confuse whatever investigator comes investigating your crimes

and as for the two hundred or so creatures that are immune, they are mostly undead, constructs and extraplanar entities, creatures that you (the player) can create and summon. And it also makes this spell an great tool for dungeon masters, who are now able to give this spell to creatures who are immune to its effects, imagine a lich just popping this spell on the spot where he stands and just creating an 30ft bubble of death where all who stands within will perish, forcing people to ether give up and try again later, make him loose concentration, something that is pretty hard to do especially with RAW interpretations of the rules where it is impossible for an lich to loose concentration due to damage unless that damage is 24 or higher, try and fight him without getting within 30ft of him or jump headfirst into the deadly zone of death where you will quickly decay.

 I did miscalculate when I made that statement. The level 7 cleric would need a +5 WIS and the tarrasque needs to be restrained to kill it with sacred flame in 10 minutes. My point was, if you have the enemy thoroughly trapped or captured, you shouldn't need to use more resources.

I think it would be a bad idea for a lich to stand in the middle of sickening radiance. It would nuke itself in around 12-16ish turns (less than 2 minutes) not counting damage by players.

Quote from ftl >>

It’s not overpowered because it’sa combat spell. Combats rarely go that long. I can’t remember the last thing in combat that an enemy stayed in an AOE spell of ANY kind for more than 3 rounds without dying or escaping.

Note that sickening radiance does not prevent the enemy from leaving at all, so they can just walk out of the area! So to restrain them you need a second spell caster. And they have to fail THAT save too. 

So yeah, a creature that is under the continuous effect of two spells for more than 6 rounds is gonna die. That’s honestly on the slow side, typically in combat enemies should be killed way faster than that.

I don’t look at it as a combat spell personally. I look at it as a utility spell. “Hey let’s get past that sleeping guard without waking him” (your caster) “I have a better idea” casts spell

even better, you can then climb up your “handy ranger”’s rope trick. And hide in a different dimension.

Quote from Robazathus >>

Quote from ftl >>

It’s not overpowered because it’sa combat spell. Combats rarely go that long. I can’t remember the last thing in combat that an enemy stayed in an AOE spell of ANY kind for more than 3 rounds without dying or escaping.

Note that sickening radiance does not prevent the enemy from leaving at all, so they can just walk out of the area! So to restrain them you need a second spell caster. And they have to fail THAT save too. 

So yeah, a creature that is under the continuous effect of two spells for more than 6 rounds is gonna die. That’s honestly on the slow side, typically in combat enemies should be killed way faster than that.

 

I don’t look at it as a combat spell personally. I look at it as a utility spell. “Hey let’s get past that sleeping guard without waking him” (your caster) “I have a better idea” casts spell

even better, you can then climb up your “handy ranger”’s rope trick. And hide in a different dimension.

 
Characters wake up when they take damage.

Quote from Cyb3rM1nd >>

Quote from Robazathus >>

Quote from ftl >>

It’s not overpowered because it’sa combat spell. Combats rarely go that long. I can’t remember the last thing in combat that an enemy stayed in an AOE spell of ANY kind for more than 3 rounds without dying or escaping.

Note that sickening radiance does not prevent the enemy from leaving at all, so they can just walk out of the area! So to restrain them you need a second spell caster. And they have to fail THAT save too. 

So yeah, a creature that is under the continuous effect of two spells for more than 6 rounds is gonna die. That’s honestly on the slow side, typically in combat enemies should be killed way faster than that.

 

I don’t look at it as a combat spell personally. I look at it as a utility spell. “Hey let’s get past that sleeping guard without waking him” (your caster) “I have a better idea” casts spell

even better, you can then climb up your “handy ranger”’s rope trick. And hide in a different dimension.

 
Characters wake up when they take damage.

 Wake up yes. Instantly know what causes it. No.

so, usually before they figure out what’s going on. Speed gets halved. And if you’re lucky, before they are out of it. They are at 3rd level of exhaustion. And that’s assuming they figure out that it’s sickening radiance after the 2nd level takes effect.

”dim greenish light”

not very visible when there’s a brighter light source.... but that’s only based off my knowledge of how light and the visible spectrum works, doing a lot of spectrophotometer scans and analysis, working with particle physicists for my day job.

Quote from Tim >>

I agree with your interpretation of how the spell works but I don’t think that it’s overpowered in the slightest. 

1. When you make your save you don’t suffer from any effect. Compare that to other spells where when you make your save you take half damage.
2. The Spell is visible so it’s easy to avoid going into its area when you’re not already in its area. 
3. There isn’t anything holding you in the area of the spell so it’s easy to move out of the area of the spell. 

I think that it’s a great spell when you’re working with a team mate who can either move opponents into its area of effect or immobilize opponents who are in its area of effect, but without that teamwork it’s nothing special. With that teamwork it’s devastating!

 I agree that, under certain circumstances, this spell is pretty much a certain win. There's one thing though - as far as I understand the spell's description, you can save to avoid the damage, but you are guaranteed to suffer from the other effects each round. I might misinterpret this though. Also, if you're looking for a stable way to keep the enemies in place, Wall of Force may be your best bet. I think it's safe to assume that the ability to escape a circular Wall of Force is even more uncommon than the ability to counter flight. Also, the fact that the area is visible changes nothing since you're going to place it so that the targets you want to take out are already inside anyway.

this + forcecage or wall of force is fun