Yet another question about the world of Algennon and its many monsters, this one concerning Peasoupers. Basically, they are bright green slime-covered slugs the size of a human head. They have two small eyes and a few tentacles around their mouth, but are deaf. They excrete a deadly acid that dissolves most organic materials (flesh, bone, wood, cloth, etc). The acid is sticky and difficult to remove, and this allows the Peasouper to climb anything it can’t dissolve (like stone, metal, clay, and almost all minerals). Another thing: Peasoupers are born out of filthy water. Whenever wastewater accumulates, Peasouper eggs form in the dregs. This is probably due to some kind of dark magic, but who knows. And while cities can clean their streets and toilets dutifully, Peasoupers can reproduce on their own anyway, so they’re still around and dangerous. You may be asking, why are they dangerous? Because they, like most monsters, are simply hungry. And to get at food inside villages, they’ll corrode walls and sometimes cause building collapse. They can also transmit diseases, and they will often bite humans, even if they can’t eat them. Also, the people have a level of technology equivalent to medieval Europe, but let’s assume there are no magic users among them. So, given all the clarifications in this question (above and below), what is the best way to defeat a Peasouper?

Additional information:

  • Peasoupers scarcely organize. Usually, the only time you see them congregate is when they mate.
  • Their slipperiness makes them very hard to be harmed by traditional weapons. Even if the weapons aren’t made of a dissolvable substance, the Peasouper is just so slimy that these attacks don’t work well.
  • Peasouper acid is strong. Just one of them can burn through a six-inch-thick piece of wood in around five minutes.
  • Also, this acid is constantly produced by Peasoupers. It POURS off of them, and as a result it’s very hard for any creature to touch a Peasouper directly.
  • A lot of people have been thinking that these monsters are slow. They are not. At its fastest, a Peasouper can travel at almost 10 km/h.
  • 2
    $\begingroup$ Do they suffer from the same vulnerabilities as normal slugs do, like salt? $\endgroup$
    – Dragongeek
    Dec 19, 2022 at 12:59
  • 3
    $\begingroup$ Do people need to defend against them? You haven't said much about their lifecycle, but they sound like scavengers who glorp around in middens and trash pits all day. What reason do humans have to fear them? $\endgroup$
    – Cadence
    Dec 19, 2022 at 13:02
  • $\begingroup$ If anything, good old fire would do. $\endgroup$
    – Vesper
    Dec 19, 2022 at 13:03
  • $\begingroup$ They sound delicious, are you looking for recipe suggestions? (Waste-not, want-not.) $\endgroup$ Dec 19, 2022 at 13:31
  • $\begingroup$ @Cadence good point, I’ll have to add that. $\endgroup$ Dec 19, 2022 at 13:40

5 Answers 5


Big Rock Splat Good

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Peasoupers are slow and not immediately dangerous. You can walk slowly away from the slug monster. You can stab it with a pitchfork or whack it with a shovel until it stops moving. This works fine for now. But do it every day, and your pitchfork or shovel quickly falls apart. Those things are expensive to a medieval peasant.

So they use something cheap. Namely a big rock. Call for Big Dan and Little Dan and cousin Jemima, and the four of us heft a lump field granite and drop it on the Peasouper. End of story.

The rock gets a little dissolved but it can be used hundreds of times. Then we find a new rock.

Between uses, the rocks are used to fertilize the fields. It turns out peasoupers -- much like real peas -- are alkaline and not acidic. When diluted by the rainfall, their slime works like quicklime.

  • $\begingroup$ love how he just turns a bloodthirsty monster into a mildly annoying bug used for fertilizer! $\endgroup$ Dec 19, 2022 at 14:37
  • $\begingroup$ Another answer has a comment of Peasoopers being able to move at 10kph. Not that easy to break distance, but still yes a good old SPLAT would be perfect. $\endgroup$
    – Vesper
    Dec 22, 2022 at 6:07
  • $\begingroup$ "Good old rock. Nothing beats rock!" $\endgroup$ May 26, 2023 at 20:34

Slug catchers

Hitting slow slugs with a big rock is a beautiful solution for any slug you see. However, you might not notice a slug dissolving your foundation, or find it's way to your stored food. They might be nocturnal and advance when you're not noticing them. A more passive solution is needed.

In a normal garden slugs can thrive. People who do not want this to happen do not make a foolproof slug defence all around. They protect in other ways. Natural predators, distraction, traps. For example, pots of sugar and alcohol. The slugs are attracted to it, after which they fall in. The glass walls of the traps prevent them from climbing out. They drown or die of alcohol poisoning.

Natural predators is probably difficult. But what you can do is to attract the slugs away from anything vital. Preferably outside of whatever you try to protect and at regular intervals so few escape you. The rest is easy. Have something that they can't dissolve line a pit. Slugs crawl towards the succulent bait. They can go over something that will dissolve as they crawl over it, causing them to fall to their deaths. If they will not die from the fall you can add horrible things to kill them. Spikes to fall, but also tiny hooks that rip them open as they go over it. You can even just drown them in water, or at least dilute their acid so much that they can't crawl out.

The only thing you need to do is replace the stuff that dissolves once in a while. A big wooden plank that several slugs can corrode though on different places for example. You could even do it with none corrosive stuff that drops down the moment a slug advances for enough. It does require more setup that a plank of wood of a certain thickness.


Nature will do it for you.

The monsters are already here, and they're us. Nature is a horrible grinding death machine fueled by a billion years of desperate struggle. Your poor helpless slug creatures are out of their league. The only reason they aren't extinct is because they reproduce by magic. They are continually set upon by all the natural predators of slugs, but a hundred times worse because they're so big and not poisonous, except of course for their acid glands. They're easy to find, they're slow, and they're a valuable target worth sacrificing time or the lives of many ants in a colony. Birds, including the humble chicken, will peck them to death, taking care not to stand in the acid. (Do you mean secretions, not excretions, by the way?) Ant colonies will eat them alive, heedless of casualties as the first waves drown in mucus biting their way to flesh. Worms will burrow into them and eat them from the inside out. Beetles will land on them and tear them to pieces. Dexterous predators like hedgehogs and racoons will rub them in dirt and scrape off the mucus before ripping them open. Preteen boys and their nostalgic fathers will splat them with big rocks.

Domesticate the valuable endangered slug monsters.

Dig a cesspit and surround it with a shallow, roofed moat containing a strong base to which the slugs are averse and which is toxic to them. Safely dispose of sewage and other biohazards by throwing it into the pit. Harvest the creatures for acid and compost what's left of them for fertilizer. Your fertile fields, low rates of water-born diseases, and finely tanned leather products will be the envy of all the lands not blessed with magic slime monsters.

  • $\begingroup$ Nope, I meant excretions. The acid literally POURS off of them. They aren’t that slow at all, either, moving at about 10 km/h at their fastest. $\endgroup$ Dec 20, 2022 at 12:25

Glass and iron flatware

Glass is pretty resistant to acid, as is iron.

The villagers use wooden polearms with glass heads to pick up the slugs and deposit them elsewhere. Polearm heads come in a variety of shapes, but they all fall into just a few categories:

  • shovels, for scooping up slugs
  • forks, for piercing slugs
  • brooms, for pushing and dislodging slugs

These are the same basic implements we use to move food from our plates into our mouths, and they've proven effective against a dizzying variety of scenarios. They're also familiar to your Victorian-era folk -- no epiphany or advanced science required.

None of these items is really intended to be used as a weapon, i.e. used to directly kill a slug. Rather, they are used to forcibly relocate slugs, from wherever they are found, into wherever we want them.

Where we mostly want slugs is dead. To accomplish that, we put slugs in pits and pools and cauldrons that we've filled with stuff like lye and bismuth, common substances that are useful in combating acid. Toss one into an iron cauldron filled with water, add a bit of lye, and stand back as chemistry ends the slug.

They can also use cauldrons containing weaker mixtures of those substances to clean the gunk off their implements, thus preserving them longer.

  • $\begingroup$ Where do these medieval peasants get glass weapons? I guess they could use those Pyrex baking dishes if they count. . . . $\endgroup$
    – Daron
    Jan 5, 2023 at 12:47
  • $\begingroup$ @Daron They make them. Glass is thousands of years old, and medieval Europe had glass-making, and according to Wikipedia they even had techniques for making large sheets since the 13th century. Individuals might not have glass windows in their homes, but I bet the ruling nobility would arrange for the provision of glass weapons if they were needed to maintain their holdings. I doubt every single villager needs to be armed; it might be sufficient to equip a few squads who have "slug duty". $\endgroup$
    – Tom
    Jan 6, 2023 at 2:10

Salt. A lot of salt. Strew it in circles around settlements if you have plenty of it. Just strew it on top of the slugs and watch them crumble up if you need to be a bit more economical. Living in areas where slugs are plentiful and salt is scarce and expensive will pose challenges and require other solutions. //Someone who has saltd a lot of slugs in their day.

  • 1
    $\begingroup$ That would be A-salt with a deadly weapon. $\endgroup$
    – Gustavo
    Dec 22, 2022 at 0:30

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