5e Homebrew Monster Monday: Bog Gulper, a creepy crawly swamp slug for D&D 5e

I like magical beasts. I think that it’s kind of neat that the world of Dungeons and Dragons isn’t just beset by all kinds of conniving, evil and scheming humanoids, but also nature itself–or the perverse mockeries of nature perpetrated by mad wizards everywhere– is actively trying to kill you. That makes adventuring dangerous. That makes the people who do it all the more badass. I don’t know about you, dear reader, but if I’m going to do some tabletop fantasy roleplaying, I’d rather play a badass.

With that in mind, I was thinking recently of how I’d make a trek through a swamp perfectly miserable, because I hate making travel easy. You see, I came up in the days when getting to the dungeon was half of the problem. I mean, I also came up in the days when it didn’t matter what the town’s name was or how we were going to get all of this treasure back there. Look, it was a confused time. But when I played with a Dungeon Master who wanted to drill into us that this whole adventuring gig was kind of not meant for the normal people with any other prospects, he deployed the drama-logue. It’s like a travelogue, but full of pain and suffering and leeches on your goolies. It worked, it made us think, it offered some opportunity for roleplay.

Now, I tend to smash-cut to the fun bits rather than linger over cold camps and needless travel description. If they want to interject some local color, or we need a setpiece, I’ll drop some in, but typically, getting there isn’t half the fun. We want to get over the boring bit, maybe have the requisite random encounter, and get to busting the dungeon. We’re all older guys (and gals) and we’ve got families and jobs and stuff, so we want to get that next bite of story or roleplay.

But there’s still that weird part of me that wants to give my players a little bit of grief every now and then. So I developed this critter for my low-level guys. It’s got a little bit of purple worm flavor, just scaled down to make life a little more worrisome. There aren’t enough CR4 things that can swallow an elf whole, after all. So, inject a little more misery into your swamps with this guy. Let me introduce you to:

Bog Gulper

Credit to Ralph McQuarrie

The swamps? Oh no, lad. We don’t have much business in the swamps these days.

Places of fetid, stagnant water and decaying plant matter are home to all manner of teeming life. Snakes, fish, mushrooms, tall trees, crocodiles, and the things that eat them all without favor or hesitation. Rubbery, undulating and bleach white, Bog Gulpers ripple beneath the standing waters of the deepest swamps, waiting for something to come within reach of their razor-toothed radulae.

Patient Hunters. It is difficult to imagine, when confronted with a ten-foot long, four-thousand pound gastropod, that it could ever remain hidden in the shallow depths of swamp pools and wetlands. Bog Gulpers spend much of their time buried in the sediment that accumulates around old-growth swamp trees, their mottled brown and white backs looking like nothing so much as a ripple of sunlight coming through the canopy above until it is time to strike. When the attack comes, it is typically the rasp of a chitinous, toothed ribbon, a mouth-tentacle called a radula.

Monstrous Devourers. Bog Gulpers are omnivorous, despite their fearsome reputation. While they are known to devour any animal or intelligent being that unwarily stumbles upon them, they are often found filtering castoffs and rotting vegetation from the swamp’s standing pools. Truly, if their considerable mass required still-squirming food, no settlement would be safe within many miles of the swamps.

Arcane Disposals. Rumor has it that the Bog Gulper came to be when wizards required ready access to a creature that could break down failed experiments. As a result, between careful breeding and leaking magical radiation, the relatively harmless magically-bred leech-slug creatures grew to titanic size. The wizards, according to legend, thrust their hands into their pockets, and acted casually about the horror they’d unleashed upon the world. Presumably, they stuck to less dangerous creatures from then on. Like owls. And bears.

Bog Gulper

Large Magical Beast, unaligned

  • Armor Class 15
  • Hit Points 86(9d10 + 36)
  • Speed 20 ft, 40 ft swim

17 (+3)10 (+0)18 (+4)5 (-3)8 (-1)7 (-2)

  • Damage Resistances Fire, Acid, Bludgeoning
  • Condition Immunities Poisoned
  • Senses passive Perception 14, Blindsight 60′ while in water.
  • Languages
  • Challenge 4 (1100 XP)

Amphibious. Bog Gulpers can breathe water or air.

Siege Monster. Bog Gulpers deal double damage to vehicles and structures.


Multiattack. A Bog Gulper makes two attacks, one slam and one with its radula.

Radula. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 12 (2d8 + 3) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 14 Dexterity saving throw or be swallowed by the Bog Gulper. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the worm, and it takes 10 (3d6) acid damage at the start of each of the Bog Gulper’s turns.
If the worm takes 15 damage or more on a single turn from a creature inside it, the worm must succeed on a DC 18 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the worm. If the worm dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Slam. Melee Weapon Attack: +7 to hit, reach 5ft., one target. Hit 10 (2d6 + 3)

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