Chasme in DnD 5e: Stats, Player and DM Tactical Guide

There are plenty of demons out there in the D&D mythos, and all deserve fear. Today, we’re going to be talking about one such creature that is feared by other demons and citizens of the Forgotten Realms alike.

“As you are roaming the abyss you hear a horrible droning noise. As you try to decipher whether you’re hearing the beating of wings or the screams of hundreds, you begin to slip out of consciousness.

The last thing you see before you fall to the floor is what appears to be a giant fly approaching you.”

That’s right, this article is diving into the absolutely disgusting demon known as the chasme.

What Is a Chasme?

A chasme is a category 2 demon that resembles a giant fly with some humanoid characteristics. These foul creatures are sadistic beings that live to torture others, be that a traitorous demon or a wandering adventurer. 

Chasme

Large Fiend (demon), chaotic evil

AC 15 (natural armor)

Hit Points 84 (13d10 + 10)

Speed 20 ft., fly 60 ft. 

STR: 15(+2) DEX: 15(+2) CON: 12(+1)

INT: 11(+0) WIS: 14(+2) CHA: 10(+0)


Saving Throws: Dexterity +5, Wisdom +5

Skills: Perception +5

Damage Resistances: Cold, Fire, Lightning

Damage Immunities: Poison

Condition Immunities: Poisoned

Senses: Blindsight 10 ft., Darkvision 120 ft., Passive Perception 15

Languages: Abyssal, Telepathy 120 ft.

Challenge Rating: 6 (2,300 XP)


Drone. The chasme produces a horrid droning sound to which demons are immune.

Any other creature that starts its turn within 30 feet of the chasme must succeed on a DC 12 constitution saving throw or fall unconscious for 10 minutes.

A creature that can’t hear the chasme is not affected. The effect on the creature ends if it takes damage or if another creature takes an action to splash holy water on it.

If a creature succeeds on its saving throw or the effect ends, it is immune to the drone for the next 24 hours.

Magic Resistance. The chasme has advantage on saving throws against spells and other magical effects.

Spider Climb. The chasme can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.


Actions

Proboscis. Melee weapon attack: +5 to hit, reach 5 ft., one creature. Hit: 16 (4d6+2) piercing damage plus 24 (7d6) necrotic damage, and the target’s hit point maximum is reduced by an amount equal to the necrotic damage taken.

If this effect reduces a creature’s hit point maximum to 0, the creature dies. This reduction to a creature’s hit point maximum lasts until the creature finishes a long rest or until it is affected by a spell like greater restoration.

One of the unfortunate things about D&D is that creatures with terrifying appearances tend to back that up with terrifying abilities.

The chasme definitely fits the bill, bringing us a creature that can knock an entire party unconscious on some bad rolls. 

Not to mention, it packs the all-to-common ability to reduce a target’s hit point maximum. This is never good, especially when the end result of such an entanglement is often death.

To make matters worse, that’s the only attack it’s going to be making, so players would be wise to swat one of these bad boys before things get very bad very fast.

Like most creatures, chasme have gone through some creative changes since 1st edition D&D.

The original version looked much more like the upper half of a man stitched onto the body of a giant fly.

The only thing keeping it from feeling like the minotaur’s gnat-ridden cousin were large compound eyes commanding most of the chasme’s face.

Now, chasmes have become a bit more attractive, and they basically just look like flies with a large drill-like stinger for a nose and a very out of place mullet on their insectoid heads.

It’s not a huge improvement, and all versions, including everything in between, are the stuff of nightmares.

In fact, chasme deeply resemble Gaiman’s depiction of Beelzebub, the fly-demon lord from the Sandman comics. There’s no deep importance to this, I just think it’s neat.

Aside from grotesque appearances and vicious abilities, chasme actually have some pretty fleshed-out lore. In the hierarchy of demons, while they might not be the strongest, they are definitely the first called upon to be torturers. 

These creatures just absolutely love making things suffer, so they serve as interrogators, taskmasters, and torturers for greater demons.

These kinds of positions are perfect for the fly-demons, since the one thing they care more about than torture is self-preservation.

Chasme won’t go out of their way to charge into battle like some of the more bloodthirsty demons out there. Instead, they’ll follow orders and save their own carapaces, whatever that means in the situation.

Their abilities support this cowardly approach to life. Rather than get into a full-on combat, they can fly in and attempt to knock out creatures with nothing but the horrid sound of their wings.

They might then fly off with the creatures to a secondary location or stick around and suck the life force right out of their unsuspecting victims.

More than a few adventurers have awoken to the hideous figure of a chasme looming over them. With any luck, that won’t be what your first encounter looks like.

Chasmes From Behind the DM Screen

If you’re looking to run a chasme in an upcoming encounter, your players probably deserve it, and I understand. I’m here to help you make this encounter is as terrifying as possible, playing to the chasme’s strengths.

First off, chasme are CR 6 creatures, but they probably won’t be alone, making them the centerpiece of a good encounter for a group of adventurer’s anywhere from 8th to 12th level.

At earlier levels, you might want the chasme to be the leader of some minions, and at higher levels, chasme can easily be the minions for something like a balor.

Chasme thrive on being able to move around nimbly and will prey on the weak as often as they can.

Chasme do enjoy a good fight, but the stats as written in 5e don’t support them running face first into combat.

Rather, with the stats we have, chasme should probably hang back until their minions have done the dirty work and they can sink their proboscis into their prey.

A simple RAW 5e solution is just to disregard the chasme’s self-preservation and send in a small swarm of three or four with some manes as extra meat shields, and just let the dice fall where they land.

This isn’t the worst solution, and even just a couple of chasme can become a serious threat in a single turn. You see, chasme, like many demons, have the ability to summon other demons.

The chasme summon none other than one more chasme to the battlefield. Fortunately for your players, a summoned demon isn’t allowed to summon other demons, otherwise this would go from bad to worse to actual hell.

As it stands, the combat for a chasme is a pretty challenging encounter.

Not only do your players have to worry about going unconscious, but they have to deal with flying creatures that can drain their life force. It’s definitely going to be a memorable experience.

You know what though, I think we can make it even better.

Making a Better Chasme

Chasme aren’t bad creatures, but they’re missing some things that just make sense.

The big red flag for me in the stat block is seeing only a single attack option. Sure, it’s a deadly attack, but it’s going to feel very repetitive. 

The second thing we should notice is just how easy this thing is to kill. Goblins, with a CR of ¼ have an AC of 15. Their hit points might seem like a lot, but there are plenty of CR 6 monsters with almost double that amount of life.

We don’t want to completely overhaul the creature, but we want to make them more of a threat. Otherwise, our players will make quick work of them, and this combat encounter will feel like a filler episode.

Here are my basic proposals:

  • Increase AC to 17.
  • Add in a claw attack and a bite attack for some variety.
  • Give it a multiattack with two claws and a bite.
  • Add a temporary hit point clause to the proboscis.

The AC increase is simple; we just want it to be a little bit harder to hit. This shouldn’t seem too crazy – after all, a giant fly has a pretty thick carapace.

Next we focus on the attacks it can make, by giving it more.

The chasme has claws and a mouth full of fangs; it should be able to use those. These don’t have to be incredibly strong, as they exist for a backup to the proboscis attack.

Let’s just say that either of these natural weapon attacks are 2d6, with claws being slashing and bites being piercing. 

Putting these in a multiattack sequence gives us three rolls instead of one, meaning we might not hit each time.

That’s fine, but it gives players the knowledge that their attacks can be deadly, without being solely reliant on one giant 40-plus damage attack.

So then we move onto that big old bloodsucking horn of theirs. They’re flies, and flies drain life, so we want to have them benefiting from that attack in some way.

If we allow them to get temporary hit points equal to half the hit points a creature’s maximum is reduced by, then we make the chasme that much harder to take down. 

We can’t do that forever though because then it would just be unstoppable. So to nerf the terrifying ability we’ve just created, we’ll want to say that the chasme can’t benefit from its proboscis attack until it is out of temporary hit points.

In doing this, we are essentially putting its deadly attack on a recharge. It’s going to happen again and again, but not if the players aren’t attacking it to bring that life total down. 

So let’s take a look at our new chasme.

We no longer have a flying creature that avoids combat until it can land a big hit. Now, we have a creature that gets into the fray and attacks as much as it can.

It still uses its massive flight speed to move around, but now that’s just so it can get to the juiciest piece of meat on the battlefield.

It’s going to be a lot harder to take this creature down, but it’s not any more deadly.

We’ve balanced out the terrifying proboscis attack with some standard melee attacks and put its bloodsucking potential on a recharge, giving our players time to react to what just happened and hopefully get in some serious damage before we start back up again. 

The chasme is a great example of a creature that, while terrifying, has a lot of room for improvement as it currently stands in 5e.

If you choose to take this creature at face value or if you choose to modify it to fit your needs, you’re definitely in for an interesting encounter with some terrifying demons.

As always, happy adventuring.