Odds & Ends

Tunnels & Trolls & Thieves' World

I don't know what system I'll end up running Thieves' World with, but one contender is Tunnels & Trolls 5th Edition, because the box set already includes stats for it, and I've been wanting to try it out anyway. (At least I think it's 5th Edition, since that was the most recent version of the T&T rules at the time of release.) If I go with T&T 5E, I'll probably implement the following house rule that I nicked from 7th Edition: Warriors increase their combat adds by their character level.

Carcosa Mini-Appendix M (for Movies!)

1. At the Earth's Core (AKA MST3K Experiment 1114)
2. Conan the Barbarian/Conan the Destroyer/Red Sonja
3. Conquest
4. Fantastic Planet
5. Krull
6. Riddick
7. Starcrash (AKA MST3K Experiment 1106)
8. Yor, the Hunter from the Future

Forget Yor; Pag is the real hero.

Super-Casual 2: Greyhawk Bugbearloo

Remember that new group that wants me to run D&D for them? I'm considering the following series of adventures for their campaign, in the style of my current group's Super-Casual Pulp Campaign. It'll be set in my (lightly researched, "non-canon" version of) Greyhawk, and I'm mostly using it as an excuse to run interesting modules I couldn't fit comfortably into the first Super-Casual syllabus, especially adventures by TSR UK.

Prison of the Hated Pretender
UK5 Eye of the Serpent - Level 1

N1 Against the Cult of the Reptile God - Levels 1-3

U1 The Sinister Secret of Saltmarsh - Levels 1-3

U2 Danger at Dunwater - Levels 1-4

U3 The Final Enemy - Levels 3-5

UK2 The Sentinal - Levels 2-5

UK3 The Gauntlet - Levels 3-6

UK4 When a Star Falls - Levels 3-5

UK6 All That Glitters... - Levels 3-5

UK1 Beyond the Crystal Cave - Levels 4-7

I2 Tomb of the Lizard King - Levels 5-7

WG4 The Forgotten Temple of Tharizdun - Levels 5-10

S4 The Lost Caverns of Tsojcanth - Levels 6-10

UK7 Dark Clouds Gather - Levels 7-9

I8 Ravager of Time - Levels 8-10

EX1 Dungeonland - Levels 9-12

EX2 The Land Beyond the Magic Mirror - Levels 9-12

WG5 Mordenkainen's Fantastic Adventure - Levels 9-12

WG7 Castle Greyhawk - Levels 0-25 (multiple adventures to fill in any "gaps")

WG6 Isle of the Ape - Levels 18+

Lost Carcosa and Barbarian Prince

Look at that beautiful hex map! And it's got enough types of terrain to match all of the major regions of the setting presented in Lost Carcosa, provided I get a little creative. Honestly, I'm probably going to be too lazy to draw my own hex map, not to mention that my illustrative talent is...modest, let's say. Why not borrow the Barbarian Prince map and just make some substitutions?

Open Countryside=Forest

Farmland=Plains

Forest=Jungle

Hills/Badlands=Colour-Blighted Wastes

Mountains=Underworld

Desert=Desert

Swamp=Sea

The Carcosan Underworld is supposed to be its own separate hex map, but again, I'm lazy, and I don't know if I'd have enough major underworld locations to require a second map anyway. My justification for using the underworld as a terrain type on the "overworld" is that the mountains of Carcosa are basically impassable aboveground. They're cartoonishly steep, incredibly treacherous, exposed to the elements, devoid of edible food and potable water, and in many cases airless and radioactive because they poke out through the atmosphere into space. (Maybe the atmosphere ends at a lower "ceiling" than it does on Earth, or maybe the mountains are just that tall.) Even the parts within the atmosphere are shrouded in toxic gas or blasted by eldritch energies or just really cold and slippery. Bottom line, the only practical way to traverse the mountains is the go under/through them, so moving across mountainous hexes means travelling underground for that leg of one's journey.

As for the named locations on the Barbarian Prince map, I'll probably keep a lot of them as-is, only renaming things as needed when placing specific destinations from Lost Carcosa. My main struggle is figuring out where to put the city of Carcosa itself and the Lake of Hali. Maybe the latter could lie to the south just off the map, with the "Samain Marshes" becoming an inlet of Hali, and "Aeravir Castle" becoming the city. I might change hexes 1723 and 1823 from "open countryside" to part of the inlet as well, so that it's more obvious that the city is right on the edge of Hali.

Mega-ish Dungeon?

I've been trying to make a big dungeon, on-and-off. I hesitate to call it a proper "megadungeon" because I don't yet know if it will fit all of the common criteria like "being the only or primary dungeon of the campaign" or "not capable of being completely and permanently cleared out by the players" or "being a living, constantly evolving place full of factions." Still, it's twelve floors deep, it's under a town, and I'm trying to make it nonlinear, so I feel like it's at least pseudo-mega.

When it comes to drawing dungeons, not only do I lack artistic talent, but I'm also usually hit by instant decision paralysis. To overcome this, I started with these geomorphs by Dyson Logos, helpfully arranged by my wife Jess in a manner both artistically pleasing and conducive to the creation of branching paths. Next, I implemented one of the dungeon's two major gimmicks, which I'll cover shortly. Then I examined the paths on each floor to see which areas were continuous and which were separated and inaccessible to each other. I changed a few details, mostly adding doors so that whole floors would be continuous, but sometimes leaving a separate area accessible only from another floor without magic or excavation. Finally, I picked where I wanted to put stairs - or maybe teleporters or just open shafts, I haven't decided yet.

So the absolute basics are done, more or less. I might add more entrances/exits on other floors; currently I only have two entrances between the town and the first level, although in my defense I did try to make one path down multiple sets of obviously-nearby stairs going pretty deep into the dungeon for quick access to lower levels. Then there are other stairs scattered about each floor to make less obvious linkages.

The dungeon's first gimmick is that the north and south edges of each floor are linked, as are the east and west edges. For example, if you go down a hall that leads off the map to the west, you'll loop seamlessly to the map's east side, at the same location on the north-south axis. Each floor is effectively a torus, except that this doesn't apply to the up-down axis. It's like how the world map works in a lot of older JRPGs. And no, of course I wouldn't tell this to my players ahead of time.

The second gimmick is actually one I haven't decided to include for sure, but it's tempting. The usual scale for old-school D&D dungeon maps is 10 feet per square, while Wizards of the Coast-era maps tend to use a scale of 5 feet per square. For this dungeon, I think I might go with 20 feet per square instead. Why?

• It would give me very big floors on very compact maps.
• It would make the conditions a little less cramped for big parties and big battles.
• It would make it feel more realistic to me that there are tons of monsters hustling around down there to serve as random encounters.
• It would give the denizens (both factions and loners) more breathing room and more territory to fight over.
• It would let me fit more furnishings and other stuff in each square.
• It would help bigger monsters get around more easily.
• Hopefully it would help inspire a sense of wonder in any explorers if even the hallways and doors and such are on a larger-than-human scale.

Anyway, I'm just trying to make something fun, not publication-worthy. I think it's good practice, and it would be nice to run a creation of my own again, even if it's not very original. Plus I can use it to see what those default random encounter and treasure tables in the D&D rulebooks are like in actual play; I almost never use them because I'm always running modules with their own tailored encounters and treasure instead. This could almost be like a "default" D&D adventure, straight from the rulebooks, which feels weirdly fresh since I'm not used to running the game without modules.

Pictures courtesy of https://deathgenerator.com/#faxanadu

The Truth About Pickles

It's not actually a pickle unless it comes from the Pickle region of France. Otherwise, it's just a sparkling cucumber.

Mind's Eye - A Magic Item

Part wildlife tagging/remote surveillance program and part series of field experiments, the Mind's Eye Project was instituted by the Rigellian Empire* as a means of testing the biological, psychological, and sociological effects of high-level magic use on humans. (It also doubles as a handy spy network should the surveilled population get rowdy.) Just find an isolated world infested with humanity,** implant some pre-selected individuals*** with "Mind's Eye" devices, then sit back and collect your data.

Outside of the human body, a Mind's Eye looks like a silver lozenge inscribed with the alchemical symbols for "digestion," "projection," and "the Philosopher's Stone" inscribed in gold. When swallowed, the nanomachines which make up the lozenge are triggered by the subject's stomach acid to separate and travel through the bloodstream to the brain, where they reform into a shape resembling a miniature goat's eyeball rooted directly to the visual cortex and connected to the rest of the brain by an extensive network of neural filaments. This process takes d6-1 turns, with a result of 0 meaning it takes d10 seconds instead. Upon completion, the effects listed below manifest in the subject.

If removed from the brain, the eyeball-like mass will reshape itself into its lozenge form over the course of about ten seconds, at which point it can be installed in another host. Mind's Eyes are almost never found in their lozenge state "in the wild," but rather in the brains of the most powerful and ambitious wizards in the land. This is presumably the origin of the stereotype that sorcerers are all brain-eating cannibals.

In it's lozenge state, a Mind's Eye is about as resistant to damage as steel, although it can be "tricked" into separating into a swarm of nanomachines by exposing it to stomach acid outside of a living human, at which point it becomes vulnerable to a variety of other caustic substances, extreme heat or cold, or even simple dilution and separation of the nanomachines to the point that they lose wireless communication with each other and shut down. If attacked directly in its eye-like state, a Mind's Eye has 8 HP and regenerates 1 HP every ten minutes. Killing the subject will not damage the Mind's Eye, simply causing it to revert to lozenge mode.

Effects

• Increases a character's spellcasting ability by one level. This is for purposes of spells per day, spell levels that can be cast, and the caster's level for the purposes of spell effects.
• This does NOT increase the character's level in any other way; it does not grant additional HP or better saving throws or a better attack bonus, it does not change the character's current XP or the amount required for the next level, and it does not allow the character to survive an extra level's worth of being level drained.
• This DOES allow characters to exceed any normal level cap or XP limit for purposes of spellcasting. E.g. A ninth level Magic-User with one Mind's Eye can memorize and cast spells as if they were a tenth level Magic-User, even if ninth level is usually the maximum achievable level in your game.
• This DOES allow members of other character classes and even level 0 characters to memorize and cast spells. E.g. A fourth level Fighter with one Mind's Eye can memorize and cast spells as if they were a first level Magic-User.
• Any character with at least one Mind's Eye can cast spells from scrolls, wands, and staves.
• A human character can only use up to 10 Mind's Eyes at once. Attempting to install 11 or more simultaneously is instantly and invariably fatal to humans.
• Naturally, the referee is free to reduce this amount if desired. E.g. If I were running BX D&D and I had set a level cap of 9 for Magic-Users, I would probably limit the simultaneous use of Mind's Eyes to 5 because the Expert Set only lists the class' level progression up to 14.
• Anything seen by the subject is transmitted to a recording device possessed by the Rigellian Empire, on which it can be played back and otherwise manipulated like standard video footage (albeit in binocular form).
• The current generation of Mind's Eye technology is susceptible to a series of glitches which cause certain visual information to be redirected only to the installed Mind's Eye(s) and not the perception of the subject. For each Mind's Eye installed, a character must succeed on a saving throw vs. magical device or else lose the ability to see one of the following randomly-determined sights: 

1. Random color - Seen as gray instead.
1. Red
2. Orange
3. Yellow
4. Green
5. Cyan/Light Blue
6. Indigo/Dark Blue
7. Purple
8. Violet-Red colors (Magenta, Rose, etc.)
2. Light brighter than 2000 lux - Seen as painful white glare.
3. Light dimmer than 1 lux - Seen as pure blackness.
4. Right angles that take up more than 25% of your field of view - Seen as drastically warped to become acute or obtuse to random degrees.
5. Distances across open air or empty space more than 30 feet across - Seen as being concealed by fog.
6. Motion - Seen as a low-FPS series of still images.

*Or the mysterious otherworldly being(s) of the referee's choice, naturally.

**One can scarcely generate antimatter without blowing up a world that's absolutely overrun with Homo sapiens, and they're just smart enough to cast spells, so they make perfect test subjects.

***As determined by the variables of the specific experiment, and possibly the bureaucratic whims of the researchers' bosses, or the irrational whims of the researchers themselves if they're not very objective.

Paranormal PC Quirks

Roll a d30 at character creation:

1. When you close your eyes, you can see invisible things...and nothing else, because your eyes are closed.
2. When first clothed for the day, one pocket is always mysteriously full of sand.
3. You know one additional language, with the following caveats: You can only write it with your non-dominant hand (ambidextrous characters have a 50/50 chance of either hand being the one that can write it). You can only read it with your non-dominant eye (50/50 chance of either if you don't have a dominant eye). You can only understand it in its spoken form by hearing it in one ear (it has to be on the same side as either the hand that writes it or the eye that reads it - player's choice). You can only speak it when you bleed.
4. Your fingerprints are identical to those of every other player character who rolls this result, and to the first NPC you meet who has never been met by any player character before.
5. Any metal surface you touch is noticeably slightly warmer that it should be, even accounting for your body heat, for d10 minutes afterward.
6. Your body is just incredibly unique, and doesn't necessarily match the genetics of your parents. Your belly button is an "outie," your hair has a counterclockwise whorl, each of your hands has a single palmar crease, your blood type is AB positive/AB negative/ RH null (player's choice), you have no wisdom teeth, you have an extra rib and a preauricular sinus and palmaris longus muscles, and cilantro tastes like soap to you. Your eyes also have at least one of the following features (player's choice):
1. Complete heterochromia
2. Segmental heterochromia
3. Central heterochromia
4. Gray
7. One day of each week, no one can remember your name without some kind of exterior prompt like seeing it in writing; seeing or talking to you doesn't count. Roll a d8 for the day:
1. Monday
2. Tuesday
3. Wednesday
4. Thursday
5. Friday
6. Saturday
7. Sunday
8. Player's choice
8. Once a day, you can cause one human being in your line of sight to have hiccups for 3d20 minutes if they fail a saving throw vs. paralysis. This requires no gestures, only a deliberate mental trigger.
9. The first time your HP is reduced to 0 (or whatever amount would normally kill you), roll a d10: on a 1 or 2 you die as normal, but otherwise you regain half of your maximum HP. The next time you would normally die from HP loss, roll a d10 and only die on a roll of 1 to 3, then the next time you die on a roll of 1 to 4, and so on. The ninth death definitely sticks.
10. Your shadow is always (roll d6):
1. Darker than it should be, even pitch-black sometimes.
2. Lighter than it should be, even somewhat transparent sometimes.
3. Longer than it should be.
4. Shorter than it should be.
5. Changing size and shape subtly if exactly one person looks at it, but returning to normal before anyone else can see it or the viewer can be certain they saw anything unusual.
6. Moving dramatically when no one but you is looking at it.
11. Blood tastes delicious to you, drinking blood does not trigger nausea or cause an iron overdose, and you receive an additional saving throw with a +4 bonus against contracting any bloodborne diseases (even receiving a saving throw if you normally wouldn't get one at all).
12. You've somehow gone your entire life up to now without experiencing physical pain. This is because things that would normally cause a small amount of physical pain instead cause an equally compelling share of emotional "pain" or distress, and only things that would hurt at least a moderate amount register as "literal" pain. You've never been injured enough to overcome this pain "threshold." But now's your chance!
13. You have wildly changing luck. Whenever you fail a roll on which you don't have advantage or disadvantage, you gain advantage on your next roll. Whenever you succeed on a roll on which you don't have advantage or disadvantage, you suffer disadvantage on your next roll.
14. Your dreams always consist only of an accurate recreation of everything you experienced since the last time you dreamed. (Well, except for your very first dream, which covered everything from your birth up to that point.) You live everything twice.
15. Once per day, you can make every domesticated animal within earshot come to you and try to get you to pet them by saying "pspspsps."
16. Your ability scores are each increased by 1 point while you are exposed to sunlight. Your ability scores are each decreased by 1 point for ten minutes after you speak, with the timer resetting if you speak again during this "cooldown period."
17. There is a second consciousness or personality inside of your brain. You cannot read their thoughts except those they choose to mentally "speak" to you, and vice versa. They cannot directly control your body, but they experience all of your sensory input while they are "awake." They "sleep" the same amount as a normal person, but this never occurs while you sleep, so they experience what you miss while you slumber, and you have a period of privacy during your waking hours. Each of you always knows when the other is awake or asleep.
18. You're an expert ventriloquist and can do spot-in impersonations of the voices and mannerisms of others. Your voice can realistically imitate a variety of sound effects, too. This is all instinctual and not the result of practice. You have no original voice of your own, although you may have chosen a specific impression as your "default," and others might not know its origin.
19. You have an unerring sense of time. You'd know the exact hour even deep underground, and you can count the passage of zeptoseconds flawlessly (even if you don't know for sure what a zeptosecond is). You have perfect rhythm, naturally.
20. You can bend spoons and keys and similar small objects just like Uri Geller, except for real.
21. Your voice echoes more than usual, even in places where it shouldn't echo at all.
22. While touching another non-supernatural animal, you experience all of the creature's sensory input.
23. No insects, centipedes, millipedes, scorpions, spiders, woodlice, mites, or ticks will ever willingly bite or sting you. All venomous snakes and lizards you encounter will make biting you their number one priority, even above survival.
24. You know the exact distance and direction to one particular living being at all times. Once per week, you can change which person this is, provided the new target is within your line of sight or earshot.
25. Your outer layer of dead skin is incredibly hydrophobic, so the outside of your body is never really wet. Somehow, this doesn't seem to cause any health problems - your skin doesn't even look or feel particularly dry even though it literally is. Any clothes you wear become hydrophobic as well until removed.
26. Eldritch forces are constantly reshaping you for unknown purposes. Reroll a random ability score every day.
27. You were born under a bad sign. Pick a zodiac sign: you must behave in accordance with the worst stereotypes about that sign.
28. You've found a way to bargain with some god of chance. Once per game, you can change the result of one of your rolls to the best possible result or change the result of one roll that negatively affects you to the best possible result for you. In exchange, your next d3 rolls will automatically be the worst possible result(s).
29. Roughly speaking, you perceive orange as what others would consider blue, and vice versa. Same for the red-green and purple-yellow pairs. But how would you even know?
30. You're a p-zombie. Although you are indistinguishable from a normal human as far as others can tell, you have no sentience or conscious experience or inner life. The light's on, but nobody's home. So yeah, there's no meaningful difference between you and other characters in the game.

Appendix VG: Carcosa

Here's one more post about Geoffrey McKinney's Carcosa that I've had on the back burner. In the style of some previous posts, I made an "Appendix N-style" list of inspirational material that heavily informs my personal conception of the setting. The twist is that these are all video games. Why?

1. McKinney's Carcosa always felt very video gamey to me, and especially comparable to retro games, what with the bright colors, and the pseudo-random, almost-clashing elements, and the synthesis of fantastical imagery and computer technology, and the way the game relies on the players' imagination to fill in the blanks and flesh out the implied world.
2. A lot of video games just happen to have elements that fit Carcosa very well, through either game mechanics, through characters and props and setting details, or through the tone or atmosphere created by art assets and music and such.
3. Video games just fucking rule.

Some people look at Carcosa and see Masters of the Universe. I see sprites and polygons and hear chiptune music.

Full disclosure: I haven't played all of these myself. I don't necessarily even think all of these are good, per se. But I think every single one of these is both fascinating in its own right and an exemplar of the aesthetics, mood, tropes, and pure gonzo insanity most associated with McKinney's Carcosa in my mind. I hope something here piques your curiosity and sparks some cool ideas for your own games and imaginings, whether Carcosa-related or within even stranger realms.

Picture courtesy of https://deathgenerator.com/

P.S. Much like Carcosa itself, "Age of Barbarian," "Produce," and the Japanese version of "The Legendary Axe II" include some nudity and/or sexual content that might be NSFW or upsetting to some people. I apologize if I neglected to warn about such content in any other games listed here.

Roll d66* for Inspiration for Your Next Game:

11. Age of Barbarian

12. Alien Storm

13. Another World/Out of This World

14. Ark: Survival Evolved

15. Axiom Verge

16. Barbarian: The Ultimate Warrior/Death Sword - especially Barbarian II: The Dungeon of Drax

21. Blaster Master

22. Bloodborne (and Demon's Souls and Dark Souls to some extent)

23. Call of Cthulhu: Dark Corners of the Earth

24. Cap'n Magneto

25. Chakan: The Forever Man

26. Eternal Darkness: Sanity's Requiem

31. Far Cry Primal

32. Generations Lost

33. Golden Axe

34. The Guardian Legend

35. Horizon: Zero Dawn

36. Kenshi

41. The Legendary Axe - especially The Legendary Axe II

42. Metroid

43. Overwhelm

44. Peter Jackson's King Kong

45. Phantasy Star

46. Rubicon (all versions)

51. Rygar - especially the NES version

52. The Sacred Armour of Antiriad/Rad Warrior

53. Secret of Evermore

54. Secret Quest

55. The 7th Saga

56. Shadow of the Beast

61. Tongue of the Fatman/Mondu's Fight Palace/Slaughter Sport

62. Turok

63. Turrican

64. Weaponlord

65. Wizard of Wor

66. Zeno Clash

Extras - After you use an entry from the table above, cross it out and roll d88** on this table for a replacement entry:

11. Altered Beast
12. Alternate Reality: The City/The Dungeon
13. Barbarian and Obliterator (the Psygnosis series, not the Palace Software series mentioned above)
14. Battletoads
15. Berzerk (and Frenzy)
16. Blackthorne
17. Blade Master (Edited on 8/17/21: I originally had Terrorpods here, but this is a much better fit.)
18. BloodStorm (and Time Killers to some extent)
21. Brataccas
22. Captain Zzap/Flash Gordon
23. Conan: Hall of Volta and Conan: The Cimmerian
24. Dark Sun: Shattered Lands/Dark Sun: Wake of the Ravager/Dark Sun Online: Crimson Sands
25. Drakkhen/Dragon View and Eternam
26. Dyna Gear
27. Eldritch
28. El Viento/Earnest Evans/Anett Futatabi
31. Fester's Quest
32. Forgotten Worlds (Edited on 3/6/22: I originally had Conan: The Cimmerian here, but I combined it with the Conan: Hall of Volta entry above.)
33. Heart of Darkness
34. He-Man/Masters of the Universe
35. Hylics
36. Ikari Warriors II: Victory Road
37. Isolated Warrior
38. Joust
41. Karnov
42. Koudelka/Shadow Hearts
43. Krull
44. Kult: The Temple of Flying Saucers/Chamber of the Sci-Mutant Priestess
45. Leander/Galahad
46. Last Armageddon (and After Armageddon Gaiden)
47. The Legacy: Realm of Terror
48. Marathon/Pathways Into Darkness
51. Metal Mutant
52. Might & Magic
53. Monuments of Mars
54. Mutant Chronicles: Doom Troopers
55. Oddworld
56. O.D.T.
57. Odyssey
58. Ork
61. Perihelion: The Prophecy
62. Produce (プロデュース)
63. Purple Saturn Day
64. Quake
65. Rastan/Rastan Saga
66. Robinson's Requiem and Deus
67. SaGa/Final Fantasy Legend
68. The Sinking City
71. Space Ace (and Dragon's Lair to some extent)
72. Space Funeral
73. Space Harrier
74. Spiderbot/Arac
75. Stargate
76. Stone Protectors
77. Street Fighter 2010: The Final Fight
78. Strife
81. Sword of Sodan
82. Ultima
83. Unreal
84. Vandyke
85. Vangers
86. Where Time Stood Still
87. Wizardry (especially Bane of the Cosmic Forge, Crusaders of the Dark Savant, and Wizardry 8)
88. Xexyz

Picture courtesy of https://deathgenerator.com/

*If you're unfamiliar with d66 rolls, check out this Wikipedia entry...or better yet, check out Troika!

**This works just like a d66 roll, except with two d8s instead of d6s.

AD&D Carcosa Crawl - House Rules and Lore Ideas

I've become totally infatuated with Lost Carcosa by Tristan Tanner of the blog The Bogeyman's Cave, to the point that I prefer it overall to Geoffrey McKinney's Carcosa. I think it's only natural to compare the two, given the overlapping subject matter.

That said, I still really enjoy McKinney's Carcosa setting on its own merits, and I have a couple of old ideas for it which I haven't posted about yet. I figure I should get it out of my system before my attention totally turns to Tanner's take on the concept.

I'll be referring to both the core Carcosa book and the four AD&D hexcrawls published through Lulu.com.

AD&D House Rules

• Classes are restricted to Fighters, Clerics, Magic-Users, Illusionists, Assassins, and Monks. (I could be persuaded to include Thieves as well.) Inspired by this thread at the OD&D Discussion Forum.
• For class purposes, either ignore alignment requirements entirely, or ignore the good/evil aspect of alignment. If choosing the latter, Monks must be Lawful, and Clerics must be either Lawful or Chaotic. Maybe Magic-Users should always be Chaotic? The rest, including Illusionists, could probably choose any alignment.
• If not using the Thief class, consider allowing Fighters to use Thief abilities equivalent to their level (like this) except for reading languages, using magical scrolls, and speaking Thieves' Cant.
• Human PCs only. (Unless borrowing mutants or androids from Gamma World, perhaps? Or aliens from Empire of the Petal Throne?)
• Carcosa's sorcerous rituals can be performed by any class, rather than being restricted to a Sorcerer class. Spellcasting classes have their usual spells as well.
• Remove all aspects of sexual assault and harm to children from the rituals.
• Use the psionics system from Carcosa instead of AD&D. Multiply the chances of a PC having psionic powers by 8 (e.g. someone with 18 INT, 18 WIS, and 18 CHA would have a 96% chance).
• The damage dice for space alien weapons are d12s instead of d8s.
• Space Alien weapons may be used by Fighters, Assassins, and Monks. (Thieves as well, if the class is used.)
• Ignore the weird new "Dice Conventions."
• I'd probably ignore weapon speed factors, weapon vs. armor class adjustment, segments, helmet rules, and all that jazz. I'm on the fence about giving weapons different damage vs. different opponent sizes, as well.
• If I DO try using these rules, I'll probably need assistance from THIS or THIS.
• No training time/costs needed to level up.
• No female strength limits.
• No Read Magic, as usual.
• No spell component tracking. (They can still be present as non-mechanical "flavor" if desired.)
• Consider borrowing material from Gamma World, Metamorphosis Alpha, and Empire of the Petal Throne.

Lore Alterations and Additions

• Carcosa is either Earth in the distant future or a planet colonized by future humanity. At some point between now and the game's era, the human race has mostly split into two distinct new species through mysterious means: the Lawful high-tech Space "Aliens" and the Chaotic sorcerous Snake-Men. The former have mostly abandoned Carcosa, while the latter were destroyed by the "ultratelluric forces" unleashed by the Snake-Men when they summoned (or created?) the interdimensional reality-warping dream-city also known as Carcosa (which may also be a living idea and/or a god).
• "Brown Men" are just normal, unaltered Earthly humans as we know them in our era, the predecessors to the two aforementioned posthuman species. They may have originally arrived on Carcosa via time-travel, or they may have been recreated post-extinction by the Snake-Men from preserved genetic material and eldritch sorcery, or they could have simply continued to survive alongside the Space "Aliens" and Snake-Men all this time while somehow remaining unchanged. In short, they are the remains of "original" humanity. Thus, they have the same variety of skin/hair/eye colors found in real people today, rather than the more uniform features described in the book.
• The other twelve "species" of humans are creations of the Snake-Men, as per the book. All thirteen types of humans were used by the Snake-Men as ingredients in horrible rituals, and the latter twelve types were engineered from the "Brown Men" to enable a wider variety of sorcery than that which could be accomplished through the sacrifices of only one kind of human.
• I'm considering changing the names and appearances of the "Black Men" and "White Men" of the setting, partly to further differentiate Carcosan people from real-life racial or ethnic groups and hopefully prevent any confusion or accidental unfortunate implications, and partly as an excuse to include more super-weird people à la the Bone Men. Maybe they could be Muscle Men and Blood Men?
• A friend pointed out to me that Claytonian JP came up with better names for Carcosa's technicolor peoples in "A Carcosa Hack," found HERE. I definitely prefer the terms "Umber Men" and "Ebon Men" and "Chalk Men" for Carcosan folk over terms that have greater real-life connotations.
• B'yakhee, Deep Ones, Yithians, Mi-Go, Primordial Ones, and Shoggoths are not merely different varieties of spawn produced by "The Black Goat of the Woods with a Thousand Young." Instead, they retain their original Lovecraftian/Cthulhu Mythos origins - or at least their origins as described in the Call of Cthulhu RPG.
• If the new colors of Carcosa need to be visually depicted (for character portraits, miniatures, etc.) here's my shorthand:
• Jale = Cyan
• Ulfire = Magenta
• Dolm = Indigo

Bonus: The Keep on the Borderlands - Magic Item Conversions and Other Suggestions for Carcosa

• Amulet of Protection from Good = Half damage from all mundane attacks rather than protection from "good." Instead of an amulet it's a chemical with which the body was treated, and thus it's not "collectable."
• Amulet of Protection from Turning = Same effect, but instead of an amulet it's a chemical with which the body was treated, and thus it's not "collectable."
• Arrow +1 = Bow w/ 2d10 Arrows coated in Black Lotus Powder
• Dagger +1 = Blowpipe w/ 2d10 Darts coated in Black Lotus Powder
• Elven Boots = Night Vision Goggles w/ d6 Hours of power left
• Elven Cloak = Cloaking Device w/ d4 Hours of power left
• Hand Axe +1 = Hand Axe coated w/ 3d8 doses/hits worth of Black Lotus Powder
• Helm of Alignment Change = 3d10 doses of White Lotus Powder
• Mace +1 = Lightning Bolt Pistol w/ 3d20 shots (Beam)
• Plate Mail +1 = Reflective Armor, reflects 10 "spectral colors" of lasers as one of its electromagnetic resistances
• Ring of Fire Resistance = Space Suit w/ extra thermal protection (same effect as Ring)
• Ring of Protection +1 = Absorption Field w/ 3d10+10 HP, tuned to all colors of lasers ("Full HP" was 50, so it could be charged up to 100 HP)
• Rope of Climbing = Hand-Pumped Pneumatic Steel Cable Grappling Hook Gun.
• Shield +1 = Force Field w/ 3d10+40 HP (Full HP was 100)
• Snake Staff = Grenade Launcher w/ 3d8 Hardening Foam Grenades
• Spear +1 = Spear coated w/ 3d8 doses/hits worth of Black Lotus Powder
• Staff of Healing = Grenade Launcher w/ 3d8 Sonic Grenades
• Sword -1 = Dolm Pudding Emitter Pistol w/ d20 shots (Broken: Stuck on 360° mode, hits user)
• Sword +1 = Laser Pistol w/ 3d20 shots (50/50 chance of Pulse or Beam, random Color)
• Sword +2 = Laser Rifle w/ 3d12 shots (50/50 chance of Pulse or Beam, random Electromagnetic)
• Wand of Enemy Detection = 2d6 Insanity Hand Grenades
• Wand of Paralyzation = 2d4 Paralyzation Hand Grenades
• Potions and Scrolls remain the same.

I would place the adventure in Hex 0605 on the Carcosa Campaign Map #1. The orcs, goblins, kobolds, etc. are all heavily mutated humans transformed by the giant crystals located in this hex. Perhaps the mutation process has also brainwashed them into serving some malign, Chaotic entity of eldritch, ethereal evil; hence the name of the Caves in which the mutants dwell.

Low-Level OSR Weird Fantasy House Rules

After musing on the "common wisdom" that most OSR campaigns don't last long enough for PCs to gain enough experience points to reach levels higher than 10 or so (if even that), I was inspired to rethink my reluctance to run a campaign with a relatively low XP limit. And after reading some really good house rules over at the blogs Pits Perilous and The Bogeyman's Cave which focus on low-level play, I thought I might as well share my humble take on how I'd run an OSR game with a "weird fantasy" or "low fantasy" flavor. (I know I'm late for Halloween, but I'm actually very early for what Bogleech would call Halloween 2 AKA "Christmas.") This is heavily built from an LotFP chassis because that's what most of my previous weird fantasy house rules used on this blog, so credit where it's due, but you can hopefully use this with Basic D&D and most of its standard, popular retroclones/spinoffs/variants like Old-School Essentials or Labyrinth Lord.

General

• 3 classes only - Fighter, Magic-User, and Specialist/Thief/Rogue (or whichever term you prefer).
• All PCs begin as humans.
• No weapon/armor restrictions for any class.
• XP Limit of 300,000 - Limit of Level 9 for Fighters and Magic-Users, and Level 10 for Specialists.
• My Checkpoint XP rules are in effect.
• 7 skills - 1 in 6 chance of success by default, increased by certain Ability Score modifiers and the Specialist's skill points. A maximum score of 6 in a skill means you roll 2d6 and only fail on double 6s.
• Athletics (modified by Strength) - Climb Sheer Surfaces, Open Doors, etc.
• Search (modified by Wisdom) - Finding secret doors, Architectural features, traps, hidden items, etc. (possibly also Hear Noise/Perception check-style functions)
• Languages (modified by Intelligence) - When exposed to a language for the first time, roll a skill check to see if you know it. Characters start out automatically knowing the common language for their area. Optionally, they could also begin knowing one additional language, or two if they have an Intelligence score of 16+.
• Bushcraft - Ranger-type outdoorsy know-how.
• Sneak Attack - Damage multiplier
• Stealth - Hiding, Moving Silently, Picking Pockets/Sleight of Hand
• Tinker - Picking Locks, Disarming Traps, etc.
• Maximum possible HP given each level - no rolling for HP.
• Ascending AC: Unarmored=12, Light=14, Medium=16, Heavy=18, a Shield adds 1. Even the most heavily armored monsters probably shouldn't have an AC higher than 21.
• Fighters start with +2 Base Attack Bonus and improve by +1 per level. Others start with +1 BAB and do not improve beyond that. Roll equal to or higher than AC to hit.
• Critical hits (natural 20 on attack rolls) do maximum weapon damage. Fighters are an exception; see their section below.
• No alignment.
• If your preferred rulebook normally grants Thieves the ability to cast spells from scrolls at a certain level, use the following rules instead:
• Fighters and Specialists may cast spells from scrolls. The chance of successfully casting such a spell is equal to the character's Languages skill. Failure means at the very least that the spell was not successfully cast, but it is still removed from the scroll as if it were cast; a magical mishap may also occur at the referee's discretion.
• Specialists cast spells from scrolls as if they were a Magic-User of half their level (rounded down). Fighters always cast spells from scrolls as if they were a Level 1 Magic-User.
• Magic-Users cast spells from scrolls as usual, and do not need to roll a Languages check to do so.

Ability Scores

• Strength - Modifies melee attack bonus and Athletics skill. (Not melee damage.)
• Wisdom - Modifies non-magic saving throws and Search skill.
• Intelligence - Modifies magic saving throws and Languages skill.
• Dexterity - Modifies ranged attack bonus, AC, and individual initiative.
• Constitution - Modifies HP.
• Charisma - Modifies hiring of retainers and retainer loyalty.
• No Prime Requisites or XP modifiers.

Fighter

• Begin with an Athletics skill of 3 instead of 1 (still modified by Strength on top of that).
• Can carry 5 extra normal-sized items or 1 extra oversized item before becoming encumbered.
• Begin with +2 BAB, gain +1 every level thereafter.
• For Fighters, critical hits do double maximum weapon damage at Levels 1-2, 3x damage at Levels 3-4, 4x damage at Levels 5-6, 5x damage at Levels 7-8, and 6x damage at Level 9.
• Alternatively, if your preferred rulebook includes rules for multiple attacks, weapon mastery, feats, special combat maneuvers, etc. they should be exclusive to Fighters (with the exception of Sneak Attacks for Specialists), and they should be used in lieu of these critical hit rules.
• XP beyond Level 9 - For every level beyond 9 that the Fighter would normally receive (i.e. about every 120,000 XP after Level 9), the Fighter may increase one ability score by 1 point.

Specialist

• Hit Dice are d6.
• Begin with 8 skill points to spend as they wish, gain 2 skill points every level thereafter.
• If your preferred rulebook normally grants a "Read Languages" ability to Thieves at a certain level, ignore this in favor of the rules for the Languages skill.
• XP beyond Level 10 - For every level beyond 10 that the Specialist would normally receive (i.e. about every 120,000 XP after Level 10), the Specialist may increase one ability score by 1 point.
• If increasing an ability score would normally grant a skill point in a specific skill (i.e. Athletics, Languages, or Search), but the character already has 6 points in that skill, the character can put an additional skill point into a different skill of the player's choice instead.
• Optionally, give 1 ability score point every 100,000 XP or so instead.

Magic-User

• Begin with a Languages skill of 3 instead of 1 (still modified by Intelligence on top of that).
• Magic-Users can cast Cleric spells. All spells are now Magic-User spells.
• Magic-Users can make Protection Scrolls like Clerics.
• No "Read Magic" Spell - Read Magic is removed from the spell list. Scrolls, runes on wands and magic items, and other typical magical writing that normally requires the use of this spell can instead by read automatically by any Magic-User. This skill is considered a basic part of a Magic-User's training. Essentially, every Magic-User is under the permanent effect of a "Read Magic" spell at all times.
• No need to memorize multiple copies of the same spell.
• Example: A Level 2 Magic-User memorizes Shield and Sleep. They can cast each spell once or cast Shield twice or cast Sleep twice.
• Spells can be cast from scrolls/wands/staves that are too high in level to be memorized. Spells that are too high in level to memorize can still be scribed into a Magic-User's spellbook from a scroll or another spellbook, and thereafter be imbued into scrolls/wands/staffs at the usual cost - they simply cannot be memorized (and thus cannot be cast as one of the Magic-User's normal spells per day).
• XP beyond Level 9 - For every level beyond 9 that the Magic-User would normally receive (i.e. about every 150,000 XP after Level 9), the Magic-User may increase one ability score by 1 point.

Optional Goodies

• If you want the game to be harder, the first house rules to ditch would probably be Checkpoint XP and max HP each level. Next would be non-Magic-Users casting from scrolls (if your system allowed that in the first place), then increasing ability scores with XP.
• Regarding that last one, there's also the middle ground of giving PCs a random chance to increase an ability score every so many XP, rather than guaranteeing it; maybe they would have to roll their level or less on a d12, or they would have to roll more than the current ability in question on 3d6.
• Critical hits cut both ways, so cutting them might actually make the game easier, but I'm not 100% sure.
• Mind's Eyes should pair well with these rules. (I got the idea for this magic item by wondering how wizardly NPCs could become immune to a campaign's level cap, and if PCs could learn the secret to doing it too.)
• If you want the PCs to be bigger weirdos from the get-go, you can have them all roll for Paranormal PC Quirks at character creation.
• Here's something you might allow Magic-Users to do if you want to give the wizards in your setting a horrible tradition for settling their differences.
• If a player REALLY wants to play a Dwarf SO BAD, you could permit such characters at a cost.
• If you think Fighters need a little extra somethin' to spice them up, you could try giving them (and only them) a feature like this (or better yet, the "Mighty Deeds" of the Warrior class in Dungeon Crawl Classics). Or the Weapon Mastery rules of BECMI/the Rules Cyclopedia. Or multiple attacks. Just something else to mechanically differentiate them from other classes, you know?