Carcosa , from Lamentations of the Flame Princess  (LotFP), is a weird product. I often like weird things, and I like this one. As a physical artifact, it’s a beautiful book — easily one of the coolest looking gaming books I own. It’s subtle, understated, creepy, and its design is entirely fitting given the subject matter.
What is it?
Carcosa is a multi-genre sci-fi, horror, and swords & sorcery setting compatible with Lamentations of the Flame Princess Weird Fantasy, and by extension with most old school and OSR games (D&D, AD&D, Labyrinth Lord, OSRIC, Crypts & Things, etc.). It’s flagged for adults only, and that disclaimer is appropriate.
It’s a sandbox setting (a hex crawl), with 400 10-mile hexes, each of which features two entries (so 800 in total). It’s also a toolbox full of stuff that can be used whole cloth, dropped in piecemeal, or tweaked to suit your needs, and given its mixed-genre nature that means you can potentially use it in all sorts of games.
When I was asked if I wanted to write about Carcosa, I jumped at the chance. (I received a complimentary print copy.) I own most of the LotFP books, the LotFP Grindhouse Edition  boxed set is awesome (and its Referee book in particular stands out, as it’s one of the best GMing guides I’ve ever read — doubly so for old school advice), and as a big Cthulhu Mythos fan I liked the idea of seeing Geoffrey McKinney’s take on Carcosa.
The more of the book I read, the more I started to think about all the different bits of it I could steal for current and future games. Carcosa is a tremendous source of inspiration for GMs running all kinds of games, and it’s a neat book to pick up and get lost in — something I find very useful as a GM.
I’d be remiss if I didn’t mention the element of Carcosa most likely to disturb people: Carcosa includes dark rituals that can be performed by PCs which involve child rape. When the book came out, it was the subject of a great deal of controversy largely because of this element.
Personally, I think those rituals are there to drive home the horrific nature of the setting; they’re not presented in a salacious way, and this isn’t F.A.T.A.L. I don’t think they need to be there (the other rituals are plenty horrific), and personally I wish they weren’t, but I’m a firm believer in free speech whether I agree with what’s being said or not.
Ways to use Carcosa in your games
Right up front, the author calls out the toolkit nature of the book and highlights five ways to use it: whole cloth, as a setting the PCs are transported to, for a one-shot, as a source of bits and pieces, and as inspiration. I’d like to try it more or less as written for a session or two — it’s pretty gonzo in a dark way, and it would be a fascinating world to explore.
But what interests me most about it is what I can steal and stick straight into other games. Here’s what jumped out at me.
1. Use it as a blighted realm your players will want to escape as soon as possible
Whisk the PCs to Carcosa — equally appropriate in a Call of Cthulhu game as in a fantasy RPG — and they’re going to want to get home just as fast as they can. Carcosa is nuts. There are 400 hexes on the map (see below), and each one features two points of interest; in most hexes, one of those POIs is something awful that wants to eat you. The other is probably a sanity-blasting dungeon, alien artifact that may fry you where you stand, portal to the depths of space, or something equally bizarre and dangerous.
Make the PCs need to get from Point A, where they appear/land/fall from the sky, to Point B, somewhere reasonably far away, and then just run the book as written. Here’s what they’ll be running across:
2. Steal the rituals
Carcosa’s rituals are nearly all focused on banishing, binding, or tormenting the Lovecraftian monstrosities that inhabit the place, and the rituals would fit nicely into Call of Cthulhu, horror-tinged D&D or sword & sorcery, or even a modern game like Dark*Matter depending on the direction you went with them.
The rituals are very, very dark. As presented they’re the only magic in the game world; there are no spells in the D&D sense. Using them will change the tone of a generally non-horror campaign and enhance the mood in a horror game.
They all have deleterious effects on their casters, they don’t always work, and they often involve making tough moral decisions. Is it better to let the God of the Primal Void wander around doing awful things or to sacrifice nine human beings in a ritual to banish it? For the right group, that choice will make for one hell of a session.
Using the rituals, or a subset thereof, necessarily means using at least some of the monsters (unless you avoid all monster-related rituals, but those are the majority of them).
3. Steal the monsters
Carcosa includes monster entries for most of the Cthulhu Mythos in LotFP format; these are compatible with essentially any old school or OSR game, including D&D up to 2nd Edition. If Lovecraftian horrors aren’t your bag, there’s plenty of other stuff to choose from.
My personal favorite are the mummy brains. Occasionally, as a mummy of at least 18th level with an 18+ Intelligence rots away in its tomb, its brain stays vital and alive. And it thinks, and uses its magic to explore other realities, and over time becomes a truly awful villain.
In Carcosa, they can cast any ritual in the book without performing all of the (usually awful) ablutions involved. This makes them tempting allies for the PCs, but man would a mummy brain ally be a two-edged sword. Outside of Carcosa, they’re just an awesome gonzo villain — and one your players likely won’t expect.
4. Cull the best of the hexes
With 800 write-ups, even setting aside the shortest ones, there’s a ton of inspiration in Carcosa. Here are four of my favorites — things I’d happily drop into an old school hex crawl:
(Hex 0109) A dense network of odd trenches and carved fissures mark the earth for several miles. If diligently mapped, or viewed from a height greater than 1,000′, they appear to form the script of a long-forgotten language.
What does it say? What’s the language? Is it a clue to something the PCs are searching for? Is it a spell? An invocation to summon a god?
(Hex 0202) All that is visible of an abandoned and buried base of the Space Aliens is an intermittently blinking orange light.
A big base? A small one? Is everything inside it broken and ruined, or is there crazy alien tech the PCs can steal? Is the base actually a dungeon, a la the Barrier Peaks?
(Hex 0715) In a small cave stands an altar to Hastur. In front of the altar is a Red Man punished for daring to blaspheme He Who Must Not Be Named. The Red Man is completely petrified save for his eyes and his brain. His mouth is frozen in a scream. After centuries in this state, he is quite insane.
I can see my players spending a good hour just trying to interact with this guy, then deciding what to do about him, and then leaving the cave thoroughly creeped out.
(Hex 0911) A long line of 282 Jungle Ants marches determinedly southwest, seeking the jungle in hex 0413. They will attack only those who molest them.
Most of the POIs are described this way: briefly but evocatively. It’s a feature if you like to improvise and be surprised by what happens in the game, and a bug if you don’t. I love to improvise, so this is a great format for me as a GM.
5. Read for inspiration
This is probably my favorite aspect of the book: It’s easy to pick up, hard to put down, and I find it nigh impossible not to get inspired about something I’m working on while I’m reading it. I found myself getting out of bed, heading into my office to make a quick note on my computer about a cool idea I didn’t want to forget, and then going back to bed to read on several occasions.
Carcosa has Mythos monsters, new colors not part of our spectrum (jale and ulfire), dinosaurs, robots, space aliens, fell sorcerers, hideous monsters, weird phenomena, pervading bleakness, a twisted landscape — the list is long. It’s a packed book, and it doesn’t tend to linger on details. It’ll drive some GMs nuts, but I like that approach because it sketches just enough to fire my imagination and then leaves the rest of the imagining to me.
On the whole, Carcosa  is a neat book full of peculiar stuff; I enjoyed reading it, and I can see plenty of it making its way into my games.
It’s an intentionally weird book that has a place in my collection alongside things like Black Dog’s Spectres (which features some of the most disturbing art I’ve ever seen in a game), Vincent Baker’s kill puppies for satan (wherein you kill puppies, for Satan), and the old WFRP Realm of Chaos books, with their sex and blood and demented mutants.
If you’re curious about the man behind Carcosa, Geof McKinney, Game Knight Reviews  recently did an interview with him that’s available on YouTube . If you have questions about the book, I’ll be happy to answer them in the comments.