Sickening Radiance in DnD 5e

Spell Description

Dim, greenish light spreads within a 30-foot-radius sphere centered on a point you choose within range. The light spreads around corners, and it lasts until the spell ends.

When a creature moves into the spell’s area for the first time on a turn or starts its turn there, that creature must succeed on a Constitution saving throw or take 4d10 radiant damage, and it suffers one level of exhaustion and emits a dim, greenish light in a 5-foot radius. This light makes it impossible for the creature to benefit from being invisible. The light and any levels of exhaustion caused by this spell go away when the spell ends.

What Is Sickening Radiance?

Sickening Radiance is a 4th-level spell that creates a 30-foot sphere of dim light. This isn’t just ordinary light though. Creatures who enter or who start their turns within this area must succeed on a Constitution saving throw or take a significant amount of damage, especially for a 4th-level spell that lasts 10 minutes if you hold your concentration.

Creatures that fail this throw also shed dim light in a 5-foot radius, a nice side effect to being irradiated. This effect eliminates any benefits from being invisible since anyone will be able to clearly make out their glowing figure.

The real benefit to this spell though is the exhaustion it incurs. Whenever a creature fails the con save forced by this spell, they suffer a level of exhaustion, a rather nasty fate that gets progressively worse the more it stacks up. 

For a quick refresher, exhaustion is a condition in 5e with six levels as follows:

1. Disadvantage on ability checks
2. Halved movement speed
3. Disadvantage on attack rolls and saving throws
4. Halved hit point maximum
5. Speed reduced to 0
6. Death

These effects stack, so a creature with three levels of exhaustion can only use half of their movement speed and has disadvantage on ability checks, attack rolls, and saving throws. 

Sickening Radiance is, at the time of writing this article, the only 5e spell that can cause exhaustion, making this a pretty amazing grab if you want a 4th-level method of creating instant death for your enemies. 

It’s also particularly deadly in this spell since you really only need to get a creature to five levels of exhaustion to kill them. Once their movement speed is reduced to 0, they’re trapped, and, unless you break concentration, they’re dying within a few turns. 

In fact, once a creature makes it to level 2, it’s going to start being hard for them to avoid the effects of this spell. With only half movement speed, most creatures won’t be able to cover any more than a quarter of this spell’s diameter in a turn or half if they use the Dash action. 

Granted, half is enough to get out, but that implies a creature can easily tell where the spell ends from the inside, which isn’t quite true to reality. When you’re inside of the light, everything should just seem to be a sickly green, something that my Fallout days have proven is quite disorienting.

Still, exhaustion is bad news for anyone caught in this, and that’s not the only thing this spell has going for it.

The damage is really outstanding as well, especially when we consider just how long this spell is going to stay online. It’s hard to compare the damage output of spells cast with any specific spell slot, but we can do a bit of math to get a picture here.

We know that this spell lasts for 10 minutes, and we know that combat is 1 minute, or 16 rounds. Since this spell tracks turns, we’ll have to track rounds as long as it’s up, so that’s 160 rounds. 

Let’s be a bit pessimistic and say that we can only keep it up for 5 minutes, or 80 rounds. Even if we’re only getting one trigger each round of combat, that’s 320d10 damage or an average of about 1,920 points of radiant damage.

Obviously, this is insane, and we won’t be dealing that much damage. The more likely scenario is that we employ some tactics to keep targets inside of the sphere for as long as possible, likely over the course of a combat. Six turns with failing saves and a creature is dead — if they don’t die from damage alone before they get there.

So, is Sickening Radiance a good spell? You bet your irradiated posterior it is. Of course, it does have its downsides.

For one, this is a large, albeit standard, area of effect. Depending on the combat quarters, this might seriously limit your allies’ ability to move around without risking a level of exhaustion. 

The main downfall, or rather, the thing keeping this from being overpowered is that creatures that succeed in their saving throw take no effects, not even a faint glow. Typically, a successful save against a spell with damage and effects will save you from the effect but still results in you taking half the damage.

This means that the spell is completely avoidable for creatures with good con modifiers or tricks up their sleeves. A creature with legendary resistances can walk through this without so much as an eye sore. Plus, most creatures can choose to take a Dash action and quickly pass through even the largest distance this spell affects.

It’s still net positive for casting, but you should know that it isn’t a guaranteed way to kill the entire opposing force. You’ll still need good timing, a synergistic combo, and a bit of luck on your side.

When To Cast Sickening Radiance?

Sickening Radiance is a spell that, hopefully, you can rely on in many different situations to quickly eliminate a group of enemies. Of course, in order to do that, you’ll need to set up a reliable way to keep your enemies trapped within the sphere’s volume. If you or an ally can also affect a group of creatures’ saving throws, that will definitely help as well.

A rather simple combo here is to cast a Wall of Force or another clear-trapping spell immediately after casting Sickening Radiance. This combo seals a number of creatures, size depending, into a mostly inescapable space with nothing to do but make saving throws and freak out.

This combo works particularly well because both spells last for 10 minutes if concentration is held. While this would be incredibly hard to pull off in combat, it is a very real possibility if two casters manage to sneak up on unsuspecting enemies. Alternatively, it could be set up as a trap if you cast both spells into Glyphs of Warding and set WoF to trigger after Sickening Radiance.

This basic concept is great and super deadly, but it is anything but reliable since it requires some specific conditions to be met.

If you want to actually be able to use this in combat or, at the very least, as a spur-of-the-moment occurrence, it’ll be much more reliant on luck and good timing.

Spells that create difficult terrain are particularly helpful here as they effectively cut a creature’s speed in half and make it harder to escape the radiance. 

Grease and Erupting Earth are great options that don’t require concentration, with Erupting Earth maintaining the ability to do a bit of damage on setup as well. 

Spike Growth and Entangle are perfect if you have a druid in the party who wants to help out as they require concentration but have some nice additional effects on top of the difficult terrain they create.

If you can’t set up a way to make it harder for creatures to move while within the radiance, you can try some spells that push or pull creatures into the radiance post-haste. We have a lot more options here with Gust, Thunderwave, Vortex Warp, and some invocation-enhanced Eldritch Blasts coming to mind without even looking anything up. 

Reducing a creature’s saving throw is also beneficial if a bit harder to pull off. In fact, one of the most reliable ways to do so is a little spell known as Sickening Radiance. Sure, someone could cast Bane to reduce a few creature’s saves by 1d4 each, but that requires them to fail a Charisma save in the first place.

Ultimately, your best bet is to focus on battlefield control, and spells certainly aren’t the only way to do so. A martial member of the party might have ways to knock creatures prone. With the Sentinel feat, they might drop a creature’s speed to 0 on an opportunity attack, even if that means being a bit too close to the radiance for comfort.

The list really goes on quite long with all the possible ways that you can push, restrain, pull, incapacitate, grapple, teleport, trap, reduce speed, confuse, charm, frighten, etc. 

At the end of the day, the best way to cast Sickening Radiance is to make sure your party knows you’re going to take it. Unlike most spells, which you can rely on as a steady source of impacting the desired effect, Sickening Radiance is the kind of potentially overpowered sweeping effect that you’ll want to actually plan for.

Turn this spell into a group activity, a bit of an in-combat mini-game, and see just how well your party can effectively exhaust your enemies. Even if you just cast it out of the blue, you’re still likely to get some decent effects out of it.

Also, and I feel like this shouldn’t need to be said, don’t use Sickening Radiance if your only goal for it is to illuminate invisible creatures. Faerie Fire will get the job done for much cheaper with much less chance of collateral damage. 

Who Should Take Sickening Radiance?

There aren’t many classes that can take Sickening Radiance, so it isn’t so much a question of optimization, but a question of desire. Do you want to kill your enemies by unleashing what is essentially nuclear fallout? This might be the spell for you.

Obviously, access to other spells that can help in pulling this off is going to be useful. By that metric, wizards are one of the best bets. In the wizard class, you’ll also find some help with the Divination subclass. Their Divine Portent will allow you to replace another creature’s roll with one of two rolls you made at the beginning of the day, likely forcing them to automatically fail.

Sorcerers that take this should strongly consider grabbing Heightened Spell and/or Careful Spell, either hurting an enemy’s chance of saving or helping your allies who could’ve been affected while casting. Outside of that, sorcerers don’t have any specific builds that link to this spell well.

Lastly, we have warlocks. This kind of spell fits right in their genre of strange, morally grey spellcasting. So if it fits your warlock’s vibe, grab it up. Additionally, you’ll want Grasp of Hadar (10-foot pull), Lance of Lethargy (10-foot movement speed), or Repelling Blast (10-feet push) to enhance your Eldritch Blast so that you can keep creatures where you want them.

Overall Thoughts

Sickening Radiance isn’t quite an overpowered spell, but it certainly comes close if you put it in a nice combo. Sneak up on large groups of enemies, throw a big snag in combat, or have a guaranteed way to kill a big bad — no matter how you use it, it’s sure to create some memorable moments at the table.

As always, happy adventuring.