Moonbeam 5e Guide: Radiant Artillery

On a moonless night in a lonely forest, two enemies faced off, a cloaked man and a spearman. The cloaked man spoke some words and the moonlight came out of nowhere, bathing the spearman. The spearman’s flesh smoked as he shrieked in agony.

The spearman turned into a wolf and fled. The cloaked man turned into a horse and pursued, as did the moonbeam.

Welcome to a Moonbeam 5e Guide.

Bottomline on Moonbeam

Moonbeam is a 2^nd level druid evocation spell that allows you to do continuous radiant damage to those within its AOE (area of effect) for up to 1 minute.

How Does Moonbeam Work?

The caster creates a silvery column of pale light shining down. The column is a 5-foot radius, 40-foot-high cylinder filled with dim light.

Any creature that enters the AOE for the first time will have the following happen at the beginning of its turn:

• It will be engulfed in ghostly flames and experience searing pain
• It will have to make a Constitution saving throw
• On a failed save, it will take 2d10 radiant damage
• On a successful save, it will take half damage
• If a shapechanger, the victim will have to roll its saving throw with a disadvantage
• Any shapechanger that fails its save reverts back to its original form and can’t change forms until it leaves the AOE

During the turns after the spell, the caster can use an action to move the moonbeam’s AOE at 60 feet/turn in any direction for the duration of the spell. As per Player’s Handbook (PHB), here are the spell’s stats:

• Moonbeam
• 2^nd level evocation spell
• Casting Time: 1 action
• Range: 120 feet
• Components: V, S, M (several seeds of any moonseed plant and a piece of opalescent feldspar)
• Duration: Concentration, up to 1 minute
• Scalable at Higher Levels
• Damage increase 1d10 for each spell slot level above 2^nd added.

Is Moonbeam Good?

Yes. Most players, myself included, would say that Moonbeam is good.

Why?

• Radiant damage is one of the most reliable damage types in the game
• Compared to most 2^nd level damage dealers from other D&D classes, it can hold its own just within the 1^st round
• It’s a continuous damage dealer capable of doing up to 40-200 damage points to victims exposed for the full duration and 80-400 points to radiation vulnerable victims like vampires
• Its range is better than most heavy damage-dealers in the game with the exception of Fireball and some others
• It’s mobile and can be moved at a speed that is double that of most humans

To make it a great spell, however, you have to understand how druid casting works.

The Art of Druid Casting

If you want to be a walking piece of field artillery, play a sorcerer or an evocation wizard.

Playing a druid is about more than that.

Playing a druid is, of course, about nature spells and nature-oriented features like wild shaping.

Druid Casting is often about being a good concentration caster. If you want to fire and forget, don’t be a druid.

For the purposes of Moonbeam, good casting is also about movement.

Concentration Casting

When you cast a spell that requires concentration, there are things you can do and things you can’t do.

Things you can do include but are not limited to:

• Cast spells
• Move including Dash/Dodge/Disengage
• Commit a range of actions, bonus actions, and reactions
• Make ranged attacks
• Make melee attacks
• Take damage and pass a Constitution saving throw
• Experience certain environmental phenomena and pass a Constitution saving throw
• Wildshape after casting a concentration spell

Things you can’t do are:

• Cast another spell that requires concentration
• Be incapacitated or killed
• Take damage and fail a Constitution saving throw
• Experience certain environmental phenomena and fail a Constitution saving throw

So, as long you can avoid those 4 bullet points above, your concentration spells, including Moonbeam, will succeed:

If you cast Moonbeam while another concentration spell is in effect, the first spell ends. If you cast another concentration spell while Moonbeam is in effect, Moonbeam ends.

To understand fully what incapacitated means in game terms, please check PHB p. 290-292. Incapacitated includes:

• Paralyzed
• Petrified
• Stunned
• Unconscious

You can still concentrate while in the following conditions, which incapacitated does not include:

• Blinded
• Charmed
• Deafened
• Frightened
• Grappled
• Invisible
• Poisoned
• Prone
• Restrained

Constitution saving throws and environmental phenomena will require a more thorough explanation below

What constitutes “certain environmental phenomena” is completely at the discretion of a DM. The example given in PHB p. 204 is “a wave crashing over while you’re on a storm-tossed ship”.

If your druid takes the Druidcraft cantrip, you’re unlikely to encounter a storm while casting Moonbeam because you’ll have an excellent weather forecast every morning with hourly updates at your choosing.

Environmental phenomena might be an issue for Moonbeam casters that move while casting and I’ll talk about that in the Movement Casting section.

Constitution Saving Throws and Concentration Casting

For those who don’t know, the ability for challenges to your concentration, sometimes called concentration checks, is Constitution. If you have a Constitution saving throw/concentration check/Constitution check and fail your check, the spell you’re casting ends.

If you have to roll a Constitution check, you will roll a DC 10 and add your Constitution modifier to the roll. If you get a 10 a higher, you pass. If you don’t, you fail.

Therefore, if you’re casting Moonbeam and you’re made to do a Constitution check, a +0 modifier will give you a 50% chance of passing your Constitution check. For every point added to your modifier, your chances go up 5%. For every added negative modifier point, your chances go down 5%. Example:

A druid with a 12 Constitution (+1), would have a 60% chance of passing a Constitution check.

A druid with a 9 Constitution (-1), would have a 50% chance of passing a Constitution check.

If you take more than 20 points of damage, your DC goes up and you divide the damage by 2 to get the new DC. Example:

Your druid takes 30 points of damage during Moonbeam and has to roll a Constitution check. Because the damage is over 20, it will be DC 15. (30/2 = 15)

So how high should your Constitution be if you want to be a good Concentration caster?

That’s a character build question.

Building a Druidic Concentration Caster

Having a high Constitution will affect your other ability scores unless you want to roll for it. Obviously, most druid players are going to max out their wisdom, but what about Constitution?

Constitution and Wisdom

If I want to max out on Wisdom and Constitution, I would pick a hill dwarf druid.

Using the standard array (15,14,13,12,10,8), here are my hill dwarf druid stats:

This isn’t bad for a basic druid. Let’s say that this is a 3^rd level male hill dwarf named Balin. Traditional druid skills rely on Wisdom and Intelligence: Arcana, Animal Handling, Nature, Perception, Religion, and Survival.

In addition to his natural dwarven proficiencies, let’s say he chooses 2 from his class and 2 from his background. Factoring in his level and discounting tools proficiencies, his modifiers would look like this:

With these stats, my dwarf would probably choose hide armor, wooden shield, scimitar, and sling. Therefore, his combat stats would be:

This means that without modifiers, his chance of getting hit and taking damage during a Concentration spell is 30%. His chance of passing a DC 10 Constitution saving throw is 80%. This definitely isn’t a bad build for a druid that is focused on Constitution at the price of Dexterity and Intelligence.

The issue, however, is that every time you get hit you will have to roll a Constitution check. If you try to cook an enemy with your Moonbeam for 10 rounds, you better not let yourself get hit for 10 rounds. Otherwise, you’re bound to fail your check sooner or later.

If, however, I never get hit during my concentration spells, I will never fail a Constitution check.

Dexterity and Wisdom

If I want to max out my Dexterity and my Wisdom within PHB races, I would pick a wood elf druid.

Using the standard array (15,14,13,12,10,8), here are my wood elf druid stats:

Let’s say that this is a 3^rd level female wood elf named Moonbrook. Let’s also say that because of my nice Dexterity score, I want to be a little different.

Even though I have access to Pass Without a Trace Spell at 3^rd level, I might want to use that spell slot for something else. Maybe I want a druid with Stealth proficiency, so I swap Animal Handling for Stealth:

For tools proficiencies, also via background customization, I take Thieves Tools proficiency in addition to Herbalism. Because elves have certain weapon proficiencies, I’m going to choose longbow, shortsword, studded leather armor, and shield, resulting in these combat stats:

Depending on your DM, studded leather might be considered metal armor. In this case, I would have a choice between either hide armor or leather armor. Either way, my AC (armor class) would go down to 16. Talk to your DM about this when generating your character because it makes a 16 Dexterity over a 16 Constitution less attractive.

My druid kind of looks like a ranger, but with druid spells.

Moonbeam’s stats mean that without modifiers, her chance of getting hit and taking damage during a Concentration spell is 20%. Her chance of passing a DC 10 Constitution saving throw is 70%. Now I would have to decide which is the better set of probabilities

• Better to get hit 10% less often but be 10% more likely to fail a Constitution check if I do get hit
• Better to get hit 10% more often but be 10% more likely to pass a Constitution check if I do get hit

Dexterity, Wisdom, and Constitution

If I don’t want to compromise, I do have one option if I’m not going to roll.  I can use an ability score point cost array with 3 highs and 3 lows, as seen on PHB p. 13, and pick a human druid. Using the standard array (15,15,15,8,8,8), here are my human druid stats:

My human druid will be a male named Conchobar. Keeping Moonbeam’s proficiencies, his modifiers would look like this:

In addition to going down on his Nature checks 10%, his Investigation checks on illusions would also go 10% in comparison to his 2 druid colleagues.

He also won’t be doing the party’s negotiations too often. On the other hand, assuming he picks studded leather armor and the same weapons as Balin, look at Conchobar’s combat stats:

Conchobar’s stats mean that without the opponent’s modifiers, his chance of getting hit and taking damage during a Concentration spell is 20%. His chance of passing a DC 10 Constitution saving throw is 80%.

A large part of D&D strategy is cost-benefit analysis, especially with character builds, but so far, Conchobar has the best of both worlds. If it was just about ability scores, I’d probably choose Conchobar, but let’s look at Movement and some other factors.

Movement Casting and Moonbeam

To maximize this Moonbeam, your druid needs to maintain concentration for 1 minute/10 turns. The problem is that the AOE is a small, 5-foot radius, and most opponents aren’t going to just sit there and let you cook them for 10 turns.

When they try to leave the AOE, your Moonbeam will have to follow them, and that is where your movement becomes a bigger factor than it would for other concentration spells like Spike Growth and Entangle.

When will your movement casting result in a Constitution saving throw?

If you’re going to choose and maximize Moonbeam, you should have a prior conversation with your DM about his or her interpretation of environmental phenomena as it relates to concentration casting. Example:

Conchobar (my 3^rd level Circle of the Moon druid) casts Moonbeam on a werewolf. The werewolf tries to Dash out of my AOE. As a bonus action, I Wildshape into a warhorse and pursue.

The terrain turns into a forest in the mountains.

Is a warhorse running through a forest or in the mountains an environmental phenomenon in the way that a wave crashing on a storm-tossed ship is?

I don’t think so, but other DMs may disagree. Before picking Moonbeam, I would plan a ten-minute conversation with a list of terrains and animals with the simple question:

This animal dashing over this terrain, Constitution check or no check?

Dexterity check not to trip and fall, or no check?

At 3^rd level, I can’t choose flying beasts. I like warhorses better than dire wolves and black bears because they have more speed. Some DMs, however, might feel that horses are more likely to trip over rough terrain more than bears and wolves.

Do you really want to find this out in the middle of combat game-play?

My short conversation would be:

Would a warhorse Wildshape dashing in the following environments likely result in an environmental phenomenon that needs a Constitution saving throw?

• Forest
• Mountain
• Swamp
• Underdark
• Arctic
• Coast
• Desert

Repeat for all Wildshapes you want to choose in all terrains with your DM before picking your concentration spells.

Once you’ve established the environmental phenomena rules with your DM, you should have a notion of how to maximize your movement in regards to your Moonbeam in different situations:

• Opponent moves away from you
• Opponent moves towards you
• Opponent is overland
• Opponent is indoors/underground

Conchobar vs Werewolf

• Werewolf: (shapechanger)
• AC: 11 (human form), 12 (wolf or hybrid form)
• HP 58 (9d8 + 18)
• Speed 30 ft. (40 ft. in wolf form)

Damage Immunities: Nonmagical Attacks not made with silvered weapons

Round 1: Conchobar’s player Patrick tells the DM,

“When the werewolf is 60 feet in front of me, I cast Moonbeam at a point 60 feet in front of wherever I happen to be facing.”

Conchobar casts Moonbeam at where the werewolf is from 60 feet away.

Despite rolling at a disadvantage, the werewolf passes its Constitution save, takes 5 damage, and changes from its hybrid form to its wolf form as its action and moves 40 feet away. The werewolf is now 100 feet from Conchobar and 20 feet away from being out of range.

On Conchobar’s bonus action, he Wildshapes into a warhorse. Conchobar moves 40 feet of his 60 feet movement to maintain 60 feet of distance between him and the Werewolf.

Round 2: Conchobar’s player Patrick takes the Ready action and announces to the DM:

“I continue to concentrate on my Moonbeam.

If the werewolf moves away, I move after it. If the werewolf dashes away, I dash after it.

If the werewolf moves toward me, I move away. If the werewolf dashes towards me, I disengage and move away.”

The werewolf starts its turn and rolls another Constitution saving throw:

DC10 +5 (Conchobar’s total casting modifier proficiency + Wisdom) -2 (werewolf’s +2 Constitution modifier) = DC10 + 3 = 13. The werewolf needs a 13 or higher on a d20 to make the save. 8/20 = 40/100. The werewolf has a 40% chance of making the save. The werewolf rolls a 10 and fails the save.

The werewolf takes 10 damage. 10R2 + 5 from R1 = 15. 58HP -15 means the werewolf is at 43 HP.

Because the werewolf failed a save on a Moonbeam, it cannot change back to human form. That means spears, crossbows or any ranged attacks are no longer an option. If it wants to fight Conchobar, it has to move to Conchobar.

The werewolf dashes away 80 feet.

Conchobar has a Reaction because he is Ready. As a warhorse, Conchobar can dash after the werewolf up to 120 feet, but he chooses to dash 80 feet to maintain that 60 feet of distance.

Round 3: Patrick has Conchobar take the Ready action as described above.

The werewolf fails the save again, takes 10 damage, and is down to 33 HP.

The werewolf decides to fight for its life and dashes to Conchobar and enters his hex. The werewolf, cannot, however, attack on the same turn because the werewolf’s attack is an action, not a bonus action.

Conchobar disengages and moves 60 feet away.

No matter what this werewolf does, it’s a dead wolf walking. There are 7 more turns of Moonbeam for this creature. Even if it makes every save for the next 7 rounds, which it only has a 40% chance of doing per round at disadvantage, that’s 35 more points of damage to bring it down to -2 HP.

Through proper understanding of how Moonbeam works in relation to concentration casting and movement casting, Patrick was able to use a 3^rd level character to dispatch 9 HD+18 monster in possession of immunities. That’s the maximization of the Moonbeam spell!

Had Patrick chosen to be Balin the Hill Dwarf druid instead of Conchobar the Human Druid, his Dexterity would have 13 instead of 16. The werewolf also has a Dexterity of 13, so the initiative contest would have been more in doubt.

Had Patrick created Conchobar as a Circle of the Land druid instead of a Circle of the Moon druid, he would have lost a turn Wildshaping. Because Patrick made Conchobar a Circle of the Moon druid, he could Wildshape as a bonus action instead of as an action.

Had Patrick chosen to be 40 feet or closer to the werewolf, the creature could have moved into Conchobar’s hex and attacked on the same turn.

Had Patrick worded his Ready action differently and said, “When the werewolf dashes towards me, I dash away.” Instead of “I disengage and move away.”, the werewolf would have had an opportunity attack against Conchobar.

Had Patrick worded his Moonbeam casting differently and simply said, “I cast Moonbeam where the werewolf is” instead of “a point 60 feet in front of wherever I happen to be facing.”, Conchobar might not have been able to keep the werewolf inside the AOE when the creature dashed.

Why?

You can move Moonbeam at 60 feet/turn as an action. A werewolf in wolf form can dash at 80 feet/turn as its action. The werewolf could have dashed away faster than the Moonbeam could have followed.

Conchobar can’t dash and move his Moonbeam at the same time because he would need an action to do each thing.

Because Patrick stated that the Moonbeam was 60 feet from wherever Conchobar “happens to be facing”, when Conchobar moved, his point-of-view moved with him as did the Moonbeam. Therefore, Conchobar could dash and have the Moonbeam follow the werewolf at the same time.

Moonbeam Underground/Indoors

There is nothing in the spell description that says outdoors/overland only. The game is called Dungeons & Dragons. If Moonbeam didn’t work in a dungeon, it would be in the spell description.

Even though Moonbeam works in those situations too, the movement is different.

If there are hallways and turns and doors, following an opponent and keeping that opponent in your line of sight might be a problem.

Ideally, you would want to block off your opponent’s egress. The problem for druids, however, is that the druid spells for doing that, Spike Growth, Entanglement, etc., tend to be concentration spells and you can’t concentrate on those spells while concentrating on Moonbeam.

So, if you’re in a party with other casters, Arcane Lock, etc. would work well with Moonbeam underground.

Your opponent leaving your line of sight doesn’t end the spell. If your opponent is not in your line of sight at the beginning of its next turn, however, it is probably not in Moonbeam’s AOE and probably not taking damage. Example:

After 2 rounds of Moonbeam combat in a dungeon, the werewolf dashes down a hallway and turns left.

At this point, the werewolf is no longer “60 feet in front of where Conchobar happens to be facing”. Unless Conchobar can return the werewolf to his point of view by the start of the werewolf’s next turn, there will be no damage for that turn. There are currently 8 turns left for the Moonbeam spell’s duration.

When Conchobar pursues the wolf and turns left, there is another corridor that leads to a dead end and a fork, turning both left and right.

Now Conchobar has to choose and he has a 50% chance of choosing the wrong direction and losing the werewolf entirely. He has also lost the chance to damage the werewolf for that turn and now has 7 rounds left for his Moonbeam spell.

Conchobar decides to turn right and that leads down to another hallway with a locked door.

The werewolf is going to escape damage for at least another turn. Because Conchobar has the Thieves’ Tools proficiency, he can attempt to pick the lock. If it’s a simple lock, it will be a Dexterity roll and the druid’s high Dexterity will be an asset.

If it’s a complicated lock, it will be an Intelligence roll and since Patrick had used Intelligence as a dump stat, that would hurt his chances. There are now 6 turns left for the spell.

Conchobar casts Guidance cantrip for his action to help the lock pick roll.

There are now 5 turns left for the spell.

Conchobar picks the lock and opens the door.

There are now 4 turns left for the spell.

As the druid opens the door, he comes to a hallway with a dead end. The werewolf is there. Conchobar has the initiative. The werewolf is currently at 43 hit points and there are 4 turns left on the Moonbeam.

Conchobar has to decide whether to fight or run. Conchobar has a silver dagger but not other weapons or spells that can damage the werewolf. The DM has ruled that Conchobar cannot be damaged by his own Moonbeam. The werewolf is definitely close enough to move into Conchobar’s hex for melee, should Conchobar decide to stay.

Even if the werewolf takes full damage every turn for 40 points total, it will still have 3 hit points remaining and Conchobar will have to successfully stab the lycanthrope at least once to kill it.

Radiant Damage and Constitution Saves

Contrary to popular belief, most undead are not vulnerable to radiant damage, only shadows and shadow demons. Regardless, no undead or shapechangers are resistant or immune to radiant damage.

Many critics argue that Constitution saves are not reliable because most tough monsters, including undead and shapeshifters, have a high Constitution.

If your druid is a good caster, that shouldn’t matter too much.

Even vampires, who have 18 Constitution, have a relatively low chance of making their saves against Conchobar.

DC10 +5 -4 (Vampire +4 Constitution modifier) = 11. Vampires only have a 50% chance of resisting a 3^rd level druid’s Moonbeam. Vampires have an advantage on most of their saves but, as shapeshifters, they have a disadvantage when in a Moonbeam.

The disadvantage cancels out the advantage so the vampires only roll once per saving throw and thus only have a 50% chance per turn against Conchobar at 3^rd level. Obviously, Conchobar probably won’t be facing any vampires at 3^rd level so by the time he does face them, his casting modifier will be even higher.

FAQs

Conclusion

As you can see, maximizing Moonbeam spell is about making sure your opponent takes damage throughout as much of the spell’s duration as possible.

A big part of that is going to be a thorough understanding of movement, action economy, and the DMs interpretation of the rules.

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David Blanc

David is a writer and RPG gamer that has had the lines of fantasy action and reality action blur many times. Since the 1980s, David has been captivated by Dungeons & Dragons, both 1e AD&D and basic rules, and has since created his own modules.

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