The Chasme is not a very dangerous Demon. At least not if the party is high enough level to be taking Demons on in the first place. It does play an interesting role in the demonic pyramid of power and it does have a few interesting abilities that make fighting it a unique challenge. Though it does have a simple design, it is far from interesting or effective. I hesitate to say that it’s any better than the two demons I’ve discussed already, but it is more unique than ‘big red monster that kills stuff real good’.
Lore is this creature’s strongest feature. The Chasme doesn’t rule over armies, rather it serves demonic lords as interrogators or taskmasters. They exist to torture, especially to demons that desert their masters. When they return these demons to their masters, they derive great pleasure out of tormenting them without fear of being reprised.
Again: it won’t be the star of its own story. But it does serve a more interesting role in the grander demonic plotline! Perhaps the party could meet a demon turned rogue and have to defend/rescue it from a Chasme! Maybe a member of the party can get kidnapped by one, forcing the rest of the party to rush to the rescue while the kidnapped player tries to resist the Chasme’s tortures. The possibilities are limited, yes, but they make for some interesting storytelling!
Now it’s all downhill from here.
Design: Jeff Goldblum in ‘The Fly’
It’s a big fly monster. Unique for a Demon, yes. Unique for a monster? No.

Unfortunately, you can’t glean much information from its demonically unique design. Sure, you can figure out how it moves around during life and battle. But what about it tells you ‘torture master’? Nothing.
And that’s about all there is to say. It isn’t an especially great design. In fact, in terms of effectiveness, I’d argue that it’s a bad one! But out of all the demons in this book, it does stand out.
Stats: The Not-Vampire
Holy shit this thing could be a pain in the ass! Rather than having a simple set of attacks that deal damage, this monster has a collection of special abilities that reduce the party’s ability to defend themselves. If the party is having a bad day for rolling, this monster could absolutely ruin them.
In terms of defenses, this monster isn’t anything to write home about. Its AC is decently high, but not very hard to beat. Its HP pool averages out around the one hundred zone, making it time-consuming to kill. While its immunity to poison and resistance to cold, fire, and lightning damage does make it more difficult to kill, it doesn’t make it truly challenging.
The main challenge of facing a Chasme is its Drone ability. With this ability, it emits a droning sound that doesn’t affect other demons. Should any non-demonic creature that hears it fails a DC 12 Con saving throw, they fall unconscious for ten minutes. If they can’t hear the sound, they automatically succeed in the saving throw. Should a victim be hurt or splashed with Holy Water, they are freed from the effects. When they break free, they are immune to the effects for 24 hours.
While it isn’t hard to beat the DC, that ability is still incredibly dangerous in battle! Theoretically, it could take the whole party out of commission! But it still isn’t as dangerous as its primary method of attack: its Proboscis attack.
In terms of damage, this move is pretty dangerous. It does 16(4d6+2) piercing damage, along with an extra 24(7d6) necrotic damage. Said necrotic damage also temporarily lowers the victim’s total HP, reducing their ability to heal. Should that effect of the attack reduce the total HP to zero, the victim is killed. The effects can be dispelled by taking a long rest or using Greater Restoration.
This makes the Chasme incredibly dangerous! While it isn’t hard to kill, it can deal a huge amount of damage! If the party isn’t careful, keeping a keen eye on each other during the battle, they could easily suffer from some major casualties! The fight won’t last long for either party, no matter who is victorious. But it is bound to be a brutal and bloody bout!
Conclusion
The Chasme is an interesting Demon. It doesn’t have an especially good design, but they are uplifted by their fascinating lore and unique combat abilities. It is far from the best monster in the book, but it is still one of the best demons I’ve reviewed thus far.
With all that in mind, let’s but the Chasme on the Best of the Bestiary!
- Beholder
- Death Tyrant
- Couatl
- Behir
- Aboleth
- Chuul
- Chimera
- Death Knight
- Ankheg
- Aarackockra
- Azer
- Demilich
- Spectator
- Cambion
- Animated Armor
- Banshee
- Basilisk
- Bulette
- Cloaker
- Darkmantle
- Chasme <——–
- Barlgura
- Balor
- Planetar
- Carrion Crawler
- Rug of Smothering
- Bugbear Chief
- Bugbear
- Vine Blight
- Twig Blight
- Needle Blight
- Bullywug
- Cockatrice
- Solar
- Deva
- Cyclops
- Centaur
- Flying Sword
- Crawling Claw
If I were judging purely by design, this monster would definitely be lower on the list. Lore wise, on a basic level, it is on par with the Balor and Barlgura. But it manages to find the edge over its two demonic predecessors thanks to the more interesting flavor text and combat abilities. It isn’t the best demon. But it is the best we’ve seen so far.
Though that’s still not saying much.