I recently ran across a fantastic "dungeon vermin" table in one of the numerous blogs that I visit. I wish I would have taken notes so I could give credit, but I didn't. If someone knows, throw a note in the comments and I'll link back to the original post.
Below are 100 vermin encounters for the Perilous Halls of Sorrow. These are meant to be destructive, loathsome, harassing, and generally unpleasant (although a few can be run amusingly if desired) encounters. Roll 1d100 and see what horrors await the characters.
Cave Crickets: Generally the size of a large cat and easily startled, cave crickets jump and leap away from lights. Any injury is accidental as they try to escape (a single attack: init-4, atk+2, dmg: 1d8p).
Dungeon Fleas: dungeon fleas are the size of a thumbnail and infest an individual (daily Feat of Intelligence to notice). Each day a person is infested, one other person gets infested. Infested characters itch and are covered in small bites (1d4p 1hp bites each day). It takes a good cleaning to clear them out.
Giant Beetle: There are a variety of giant beetles, but they generally act per the Hacklopedia entry.
Giant Bombardier Beetle: per Hacklopedia
Giant Boring Beetle: per Hacklopedia
Giant Dung Beetle: weighing in at 50 pounds, giant dungeon dung beetles roll about huge balls of compacted monster dung. When encountered, there is a 50% they are rolling toward the characters. they move at 5+d6'' per second (adjust speed every few seconds as they adjust) and will bowl folks over for 2d4p damage if the PC's don't run. If otherwise cornered, they dung beetle will attempt to flee as they are noncombatants.
Giant Fire Beetle: per Hacklopedia
Huge Ticks: Treat as tiny versions of a giant tick from the Hacklopedia but with only 6 hp and doing 1d3p damage when they bite.
Giant Worker Ant: per Hacklopedia
Gigantic House Flies: Huge and disgusting, these flies are the size of a fist. They will ruin any food or paper (scrolls) that they land on. They are attracted to the scent of offal and carrion and will generally be irritants and pests. Of course, 5% have some sort of nasty disease.
Grave Centipede: Black with white markings that resemble a skeleton, Grave centipedes can be mistaken for an animated skeleton from a distance of in very dim light. They are the size a of a man, but otherwise as Giant Centipede per Hacklopedia
Hades Ants: while half the size of giant ants, the hades ant does just as much damage with a bite. The bite is so painful, though, damage is doubled for determining if a Threshold of Pain check should be made. In addition, Hades Ants are covered in a fine crimson "fur".
Punchflies: Punchflies aren't big, but they get moving very fast and have hard exoskeletons. They show up in groups of 2d4 and will fly into a target at speed. Each punchfly that hits roll 1d6p to determine if DR is passed - if so the target has a 1hp welt. If a target doesn't drop, they tend to move on.
Sharpflies: Similar to the punchfly, but sharpflies have extrusions that actually puncture and cut a victim. Treat them tarantubats per the Hacklopedia, except they do 1d4p damage.
Stactite Wasps: not truly wasps, but the coloration and body form could fool most without inspection. Stalactite wasps are found in small nests of 1d6. They drop down on an individual passing and cause a 1d3p hp wound if they hit (init: d8-6, atk: d20-3). A nest can often be identified by a yellowish discoloration on the floor under their nest. The they miss a target, they will slowly crawl back to their nest and wait.
Stone Eaters: Small but ravenous, stone eaters do just that - they eat through stone. The bugs themselves are rarely encountered, but their 2" diameter tunnels are. Most often the party will notice a handful of these holes, but sometimes they will reveal other aspects of the dungeon (as they are tunnels into other rooms).
Albino Rat: a totally normal rat, but ghostly white with red eyes. They are always seen solo and always way too close the someones face. The albino rat is considered a foul omen, and unless immediately killed (which is difficult because they are fast and small) something unplesant will surely happen by the next sunset.
Barfwing: These are bats that have developed a defense mechanism that causes them to reek as if they were trogoldytes. When startled, they will fly away from the party but everyone must pass a CON check as though affected by troglodyte musk (per Hacklopedia).
Cave Lizards: Always found in clustered herds of 100+1d100p, these foot long lizards are docile but spook easily. If prodded or otherwise molested, the her's instinct is to swarm over the attacker in a matter of seconds (1d4+2 in fact). From that point forward, the swarmed individual won't be able to do anything and will be crushed and suffocated in a number of seconds equal to twice their CON. Treat the heard like a swarm - for any damage done, half is also done to the target.
Dungeon Cat: a scrawny cat that will follow the party around if they feed it and hiss a warning when danger approaches (-1 to everyone's initiative). Mistreatment will cause it to urinate on a random party member's pack, making them stink terribly (and it is un-washable). This stink will attract more monsters and make hiding undetected less likely.
Giant Rat: per Hacklopedia
Huge Scorpion: Treat as a Very Large Spider per Hacklopedia but their poison paralyzes for 1d6x10 minutes. They will always be found under something else and likely have surprise.
Huge Toads: Big freaking toads looking for bugs and small rats and the like. Non-combatant. 25% of huge toads have a hallucinogenic poison they excrete for protection.
Irontooth Goat: These are goats that live in dungeons and have iron teeth. They tend to follow a party and try to eat everything (like weapons). Treat as a hunting dog per Hacklopedia if attacked it will defend itself to the death. Irontooth Goats don't flee
Malformed Mimic: Has a 50/50 chance of looking like either a very small chest that is malformed or a normal sized chest that is very poorly formed. Either way, careful observation will show that the thing is breathing. If approached, it lashes out with a pseudopod that does no damage and is only mildly sticky. No damage is done, but papers and small delicate items may be lost. Silk will definitely be ruined.
Nelbon: these are small, featherless, flightless carrion birds that are covered in weeping sores and scabberous growths. They will flee from bright lights and loud noises. They will always be found picking at some sort of corpse.
Shrieker: per Hacklopedia
Small Carrion Beast: Looking something like a tiger cub but green and having a dozen green tentacles instead of teeth, the small carrion beast generally feeds only on the dead. However, if hungry or defending itself, the small carrion beast has the following stats: hp 6+2d6, init -1, spd 2, atk -1, def +4; each attack causes 1d6 damage - paralyzation for 30 minutes (no save) if DR is passed. They are fearless and are often found in small packs of 2d4 members.
Stonen: The much maligned stonen is a gray dungeon chicken. They are encountered in flocks of 3d4 and for every 3 hens there is a 50% chance of a rooster. Roosters tend to crow and attract other critters. In general, they are repulsive but nutritious if cooked properly and easy to catch.
Tunnel Swine: small dungeon pigs, likely related to the Fell Underworld Boar found in other locations of the dungeon. They are as skittish as they are repulsively ugly, which is to say quite a bit. if caught and trained, they can sniff out special mushrooms and fungus with alarming accuracy.
Weasel: per Hacklopedia, but they live in the dungeons and are incredibly aggressive.
These creatures all carry some sort of disease and increase the virulence and lethality both by +2.
Infected Strix: Flying alone they will agressively attack a single random foe, preferring those with magical inclinations. Only those wounded by the strix will have a chance for infection.
Puking Gargoyle: These semi-permanent fixtures (they can move very slowly, but generally choose not to) squat above doorways. They vomit on anyone passing under them a maximum of twice per hour covering them in foul smelling infected goo.
Typhoid Mary: Roll for a critter that is infected but not affected. Anyone engaged in melee will have a chance to be infected.
These small creatures generally just cause problems and play tricks like unbuckling belts, tying boot laces together, or stealing small items.
Iron Mites: Weapons and metal armor are damaged or their quality is reduced by the runes carved by these whip-thin creatures. They like to wear shiny hats and tiny metal-shod boots.
Rotfaer: These obese nasties devour every scrap of food possible and replace it with glitter-laden faerie poo. They don't wear clothes and just arrange their hair and fat to cover their shame.
Stonebeards: Stonebeards tend to rip leather and papers because they don't like soft things. Blankets and fancy clothes are also on the list for destruction. They look like tiny dwarfs.
Tomb Gremlins: The worst of the lot, tomb gremlins steal things: weapons, food, bits, bobs, ephemera, spell components, anything they can get their gigantic over-sized hands on.
Giant Maggots: Other than being repulsive, these are just 1-2' long maggots squirming around looking for another bit of rotting corpse to feed on.
Rot Grubs: About the size of a thumb, the rot grub lives in piles of dung, gobs of offal, or in the bodies of the recently dead. They will burring into living flesh at an astonishing rate, making it to the victim's heart in a matter of 3d10 minutes (make a poison save vs d20p+15 or death).
Stench Grugs: These biting grubs are found nestled into piles of rotten offal or, occasionally, in treasure piles. Using the statistics for giant rats per the Hacklopedia but each wound is a stinking infected welt that takes twice as long to heal.
Tri-Mawed Stalker: With three 6" long mandibles, the tri-mawed stalker is a grub-like creature that aggressively hunts and stalks prey well beyond their actual capacity to kill them. Use the stats for giant rat per the Hacklopedia, but with +3 to attack and wounds do 3d3p-2 damage.
Molds and Slimes
Adrisax Mold: Once this starts to grow on leather (armor, backpacks, etc) is is almost impossible to get rid of. The item will be destroyed in a few days and the mold will spread. The only sure way to destroy the mold is to burn the item and, most likely, abandon everything that was in contact with it.
Bearpaws: Vaguely shaped like the paws of a large mammal, this fungus can be harvested and prepared as a meal. They show up in clusters providing 1d3p+1 days of food.
Blood Puddle: This red slime tends to cover fairly large areas (d6p+3' diameter puddle). It is harmless to anything larger than a mouse, but if stepped on a screaming humanoid face appears and snaps at the offender's legs. The face changes to the last humanoid who stepped in it.
Blue Slime: This slime acts exactly like a green slime, but does not do any damage other than making a mess on the character it has fallen on.
Cave Polyps: Large oozing pustules that seem to grow from the dungeon walls and floor. The ooze is an acid that will damage leather and other soft materials.
Ghostbeard: Phosphorescent moss that hangs in great clumps resembling scraggly beards. If harvested, it will provide light as a candle for 2 hours before fading.
Grey Mold: If infected (VF 4) the grey mold grows on exposed flesh like an old man's beard at a rate of 1d2" per day. It can't be washed off, but a bath in alcohol will take care of it. If left untreated, grey mold will eventually start growing inside the character, making them violently ill then dead.
Gripping Sludge: A character stepping into this stone-colored sludge will be held fast. A Feat of Strength (vs d20p) will allow a character to break free. This is more of an inconvenience for most, but small weapons and items may be lost or dropped into the sludge and if a character falls they will be covered in the stuff.
Lambri: Also known as elfbread lambri is edible, delicious, quite nutritious, and highly addictive. Each lambri cluster contains enough food for 10+d6p meals that fits into a single encumbrance slot. If a poison save (VF 16) is passed each time the character eats the stuff, the character is not addicted - failure and they gain the Addict quirk per the HackMaster Players' Handbook but gain 0 BP.
Memory Caps: If a character eats a memory cap (which are easily identifiable) and pass a saving throw vs poison (VF 12) they will gain a random memory from an unknown source. Failure and the character is poisoned as if by a huge spider (per Hacklopedia). The memoriesspo tend to be about the general area of the dungeon the fungus is found in.
Nifelslime: Sickly white in color and appearing as sticky clumps of plumb-sized clots, anyone passing within 5' of a nifelslime cluster will take a wound of 1d4p hp as their life energy is drained away. Those paying attention will notice the temperature drops significantly when within 10' of the fungus.
Puffball: Giant puffballs the size of basketballs that, if disturbed, vomit forth a huge cloud of obscuring spores. A poison save (VF 15) indicates no effect, but otherwise the character coughs and sputters for a few minutes and is, unfortunately, infected. Infected characters appear to have a cold for a week, but at the end of the week, they must pass a VF 6 poison save or die.
Wriggling bits of necrotic flesh from the Patchwork Kingdom are collectively called scraps. They are unfinished creatures, fragments of monstrosities, or possibly the shed skin of dying gods and demons. They come in seemingly infinite variation but a few types are more common than others.
Blubbering Scrap: They don't move much other than sitting in a disgusting pile and shuddering, bubbles forming on their mucus covering that burst and let forth a sound similar to someone crying and blubbering with absolute hopelessness.
Clinging Scrap: Hand-sized scraps that cling to whatever they can. If left long enough or undiscovered, they will move onto the flesh of their target and merge with it. The merging often causes the target to gain a strange arcane power as well as a permanent aberration.
Crawling Scrap:Often seen in small herds, these scraps crawl along the wall like inchworms or caterpillars. They can be easily avoided, but tend to leave behind a slick trail of clotted blood.
Floating Scrap: Gobbets of bloody undulating muscle, the floating scrap hovers in mid-air and pulses slowly. They move toward living creatures with alarming speed and attempt to get into their mouths, especially clerics and the particularly devout. Effects if this happens are unknown.
Small Scrap: Twitching and slapping wetly against the floor, these finger sized scraps are found in herds covering up to 400 square feet. While utterly harmless, they tend to attract scavengers and predators, the former to feed on the scraps, the later to feed on the scavengers.
These are all spiders per the Hacklopedia, just with some additional description. 90% are Big, 9% are Large, and 1% are Very Large. Whatever the size, the spiders that inhabit the dungeon are dangerous - all poison VF values are increased by 1.
Barbed Devil: The spider is covered in chitinous barbs and horns. When attacking, half the attack speed, but only every other attack is a bite (with poison) - the others are the barbs.
Hunter: These spiders will stalk prey for up to a day before attacking, waiting until the target is asleep or otherwise incapacitated before attempting to feed.
Redface: Their huge bloated abdomens are bright red with markings that look like a huge demonic face. They will often attempt to intimidate perceived threatsby backing toward the enemy.
Trap Door: Jumping out of trap doors (flagstones and bricks that have been worked loose and "hinged" with webs) these spiders improve their initiative die by 3. If their initial attack does not kill the target or there is still a threat, they will move back into their space and slam the trap door shut.
Swarms are made up of 100+d100 members that individually have little impact, but collectively can have some deadly effects. Attacks on swarms automatically hit, each point of damage done (as shield hits) to the swarm kills that many members. Fire tends to do quite a number on most swarms.
Biting Flies: Every 4 seconds everyone in the swarm takes a 1 hit point wound. A strong gust of wind will take care of these things as well.
Centipede Stampede: a stampede of huge centipedes swarm over the characters. A Feat of Agility (vs. d20p+0) will avoid damage, otherwise the characters take a 2d6p wound from numerous bites.
Landkrill: Harmless, but freaky as thousands of red, shrimp-like creatures swarm along the ceiling, walls, and floor move along at a disturbingly fast pace.
Rat King: 10 giant rats, their tales tangled and tied together, attack a single, mad creature. Each giant rat of the rat king attacks once second after another. As the giant rats are killed, the speed of the rat king attacks dwindle (5 giant rats left, attack every 2 seconds, etc.) A rat king will be preceded by a rat swarm 50% of the time.
Rat Swarm: In addition to causing a 2d4p wound every 10 seconds, the rat swarm will chew through leather, devour food, foul papers and components, and generally make a mess.
Scrap Swarm: The scrap swarm is an undulating mass of bits and gobbets of flesh moving quickly through the dungeon. Each for each character - if a 1d6p roll bypasses DR, the remaining is the percentage chance of the target picking up a aberration (magical backlash / permanent mishap).
Spider Migration: Thousands of small spiders are moving through the area. If the PC's don't move and let the migration go through, they'll be fine. If they move or otherwise act, the character is affected as though bitten by d4 big spiders. And they are really gross and tend to leave webs and egg sacs everywhere.
Swarm of House Flies: Super annoying, fly swarms hang about characters and cause a -1 attack and defense penalty as well as -10% to any skill checks. If driven away by conventional means, they have a 50% chance of appearing again the next day at 90% of their original strength.
All of these minor undead have a Will Factor of 1d3p.
Biting Head: rolling along on the ground, this is the head of a zombie which is still biting and snapping. Stats: HP 2d6, Init +3, Spd 10, Atk +2, Def -2, DR 4, dmg d4
Bone Rat: The skeleton of an enormous rat. Treat as an animal skeleton per the Hacklopedia, but with only 8 hp and doing going 1d10p damage per bite.
Bonechield: Often appearing ridiculous such as a skull with skeleton feet or a pelvis moving on a set of three skeletal hands, a bonechield is still undead and a danger. Stats: HP 1d8, Init -2, Spd 10, Atk -4, Def +4, DR 2, dmg d8
Bucca: Also called knackers and tommyknockers, these invisible undead spirits follow characters around and knock on doors and walls. Each day they follow the PCs there is a 1 in 6 chance of a random object being stolen (and hidden). Every 2 days, there is a 1 in 6 chance that the bucca will cause a wall, ceiling, or floor to collapse on the party.
Clawing Hands: Severed undead hands of humanoids, they crawl around on their fingers, leap or crawl onto PCs, and claw at faces and exposed flesh. They show up in groups of 2d4. Use giant rat statistics per the Hacklopedia, but they never run away (and are undead).
Crawling Corpse: Actually quite dangerous, a crawling corpse is the top half of a zombie. They are identical to zombies with the following exceptions: HP 8+1d8, init +0, DR 5, dmg 1d6.
Ghosthound: these spectral hounds feed on the essence of the recently dead. That are only harmed by silver weapons (which causes them to flee). They tend to follow PCs around and feast after battle. Ghosthounds are otherwise harmless to the living, but tend to bay and howl (which, of course, attracts creatures) if unfed for more than a day. Once a ghosthound attaches to the party, there is a 1 in 6 chance per day that another from their pack arrives. If a pack of 6 hounds follows the party, every day there is a chance a spectre per the Hacklopedia shows up and cause serious havoc.
Afanc Tentacle: Reaching from around some dark corner or a stinking drain, a tentacle of Afanc is thick as a man's arm and twice as strong. Treat it's appearance as an attack: Init -5, Atk +11, Def +0, DR 4. Any attack that hits had a 50% chance to grab both arms and trap a character up to 20' from the point of origin. It drags struggling victims at 5' per second and tried to pull them away (which will result in certain death). Any hit that causes damage will cause a chance of release equal to the wound out of 20 (6 point wound, 6/20 chance to release). Any hit of 20 points of damage will sever the tentacle. A Feat of Strength vs d20p+10 can break the tentacle's grasp.
Arm of Xinth: a clawed hand grabs at the characters from a puddle or works like an Afanc Tentacle, except it has a range of 5' and the following stats: Init -5, Atk +6, Def +2, DR3, dmg=grab leg & 1d4p+1, FoS vs d20p+5 to break, damage is release out of d10, 10 points to sever. An arm of Xinth carried a rotting disease on a 1 out of 8.
Carved Beast: Treat as a hunting dog of the minimum hit points per Hacklopedia. Carved Beasts are crudely carved wooden beasts poorly animated. They prowl the dungeon eating scraps of carrion and are often riddled with black wood-eating worms. They often remain motionless (-6 to initiative) and attack anyone who approaches.
Corpse Light: Winking on for only a moment, the souls of those who were killed by the dungeon make brief appearances. Some are malicious and hover over pits, others are friendly and attempt to point out secrets. They aren't technically undead, but rather the remains of living essence wrapped in a Patchwork Skein. They blink away if anyone gets within 10'.
Cousin Jack: Initially appearing as slaves or lost peasants, Cousin Jack basically latches onto a party to take advantage of their good will. In addition to never being the target of the dungeon's threats, a Cousin Jack will eat food and sap any luck the party has (1 point per day). A Cousin Jack will do anything to remain in the party's good graces without contributing. If attacked, it has the stats as a human scribe per the Hacklopedia, but "bleeds" black sand.
Dagger of Bal: Floating through the dungeon, a Dagger of Bal is a rusty old dagger that appears to be animated. It attacks anyone who gets within 20', but will otherwise stay away. Anyone who can see into the aestherial dimension will see that the dagger is just a tooth or horn extruding into this world - the body of the dagger is a bloated mass of writhing worms and pulsing bladders.
Devil's Staff: A tangled mass of hair and spittle appears to wield a gnarled bone like a staff. Treat as a human man-at-arms per the Hacklopedia.
Wiewie Nest: Most often suspended above doorways or in the corner of ceilings, a weiwei nest is a writhing knot of worm-like tubes and slick wet fibers. They will try to snatch at anything that walks under them. Mostly an irritation, but 5% of weiwei nests are immense and can grab halfling and elves to strangle them in a few seconds.
Executioner's Hood: These creatures look like black hoods worn by executioners. They drop down and immediately begin to suffocate a character (use drowning rules). Pouring alcohol or salt causes them to dissolve. Otherwise 10 hp of damage (also applied to the target) will cause the creature to die.
Fog of Slime: Not technically a slime but rather a super colony of a amoeboids. The fog of slime moves very slowly (no more than 10' per day) and can be rather huge. The fog will be 2d6px100 cubic feet. Anyone moving through it at a maximum of half rate must make a CON check (against d20p+12) for be paralyzed. This spells certain doom - in about a day. If the PC is removed from the fog within 4 hours they will wake up in 1d6x5 minutes covered in goo but fine.
Glassjaw: Attacks as a human berserker per Hacklopedia, but has a Threshold of pain of 3, a Trauma Check of 1-2, and is -5 to all saving throws.
Mosschild: This thing is apparently a contruct of moss and vines shaped vaguely like a human child standing no more than 3' tall. They are agressive and attack as a brigand per the Hacklopedia but with 2d6 hit points and damage as a knife.
Nipper: The nipper is a small creature that looks like a small stone until it opens up at which point it looks like a stone-shell clam filled with needle-like black teeth. It automatically bites at any feet that get nearby causing 1d4p-1 points of damage. They can easily be kicked away.
Oculo Imaturi: A single floating eyeball covered in slime and training a handful of red threads. 5% have the ability to charm (Mental Save vs. d20p+5). Those charmed tend to adopt the cute little fellows until they decide the best thing to do is pluck out on of their own eyes and slide in the oculo.
Tiny Trapper: Looking for all intents and purposes like a flagstone, the tiny trapper (a much smaller version of the infamous trapper) grabs and wraps around the foot. 10% of the time it will cause enough damage to ruin a boot (metal boots make an opposed d20p roll to avoid damage).
Worms and Serpents
Gorehead Asp: as asp per Hacklopedia; the head of a gorehead asp appears to be split open and wounded.
Bloodworm: Bloated worms 6-12" in length, these parasites latch on to unsuspecting victims with a small bite loaded with anesthetic. Most people don't notice until the thing has created a wound equal to it's hit points at a rate of 1hp per hour. Bloodworms have 1d4p+2 Hit Points. They are easily removed and killed.
Cistern Serpent: as rattlesnake per Hacklopedia, but this serpent lives in pools of filthy water.
Constrictor: as constrictor per Hacklpedia, but the skin is translucent. Past and current meals can be seen along with muscles, bones, and guts. Gross.
Giant Nightcrawler: The giant nightcrawler is a huge worm perhaps 10' in length. It is utterly harmless and will flee if threatened. Some claim that giant worm steaks are delicious.
Threadworms: Pencil-thin, white, and sticky, threadworms attach to exposed flesh. They do no damage but cause an irritation (-1 attack and defense for every 3 worms). Once infected (initial infections are 1d6p worms), the threadowors will lay eggs - 1d3 worms sprouting every 1d2 days for every 2 worms already infecting the character. If all threadworms and found and pulled out (each causing a 1d3p wound) the character will heal normally.
Teneborous Wyrm: Fast and deadly, a full grown teneborous wyrm is a brutal fight for survival. Luckily this is a small one. Treat as a lizardman per Hacklopedia but Fearless, 10+1d6 hit points, and doing 1d8+2 damage with a successful bite.