Curse the Darkness: A Cthulhu/Star Wars Crossover

As promised long, long ago, here’s the first in my series of crossover settings. Since I mocked the concept of a Star Wars crossover, I figured that would be a good place to start with this series. I’ll start with bringing Cthulhu into Star Wars, and then in a later article I’ll show a way to bring a little Star Wars into Call of Cthulhu.

The general assumption for the cosmology in Star Wars, or at least how I’ve always read it, is that the Light and the Dark Side of the Force exist in equal measure throughout the Galaxy. They are two sides of the same coin, meaningless without the other.

In the “Curse the Darkness” variant I’m presenting here, the Dark Side is not only a seething, mind-eroding concept that would warp the fragile little minds of those who confront it, but it’s also the normal state of being. The Light Side is merely a candle lit to keep the darkness at bay. Only the Jedi Council ever knew the truth.

What You Need

Mainly, you need the d20 Star Wars Core Rule Book of your choice. Also helpful would be d20 Cthulhu for rules adaptation and spells, The Dark Side Sourcebook for extended Dark Side fun, and Alien Anthology for help in converting d20 Cthulhu monsters into d20 Star Wars monsters.

The Lead In

First off, you need to get your players into playing. There are a couple primary ways you can do this. You could say, “Hey guys, I’m wanting to run a horror-oriented Star Wars game, using rules from d20 Cthulhu.” Of course, this may sound horribly lame to your average gamer, and earn you a deluge of rotten tomatoes. Depends on how much your players are into Mythos. However, this should work fine for big Mythos fans. But then, a big enough Mythos slut will go for anything.

The other option is that you could simply tell your players that you’re running a dark version of Star Wars, and keep track of any Mythos related rules, like Sanity Points, secretly. This could even help bypass the cliché “I burn all books and run away from anything that makes a scary noise” problem you run into with normal Cthulhu games.

General Setting

Since the dawn of Creation, the Dark Side, the Great Old Ones, or whatever you want to call it, has existed. The sentient races that form modern galactic society are infants in comparison. The 5,000-year-old republic? Nothing to the Dark Side.

Early in the days of the Republic, the Jedi formed to pursue study of the Force. They gave it pretty names and classifications, and developed a system of tapping into the Force that kept them safe, sane and happy.

But into every organization, a little entropy must fall. Factions sprung up, the most controversial of these being the Sith. They wanted to tap into the underlying power, insisting that was the only true source of truth to be found. And they were mostly right.

So, of course, there was this big rift, a big war, much falling out. You color it how you like it best.

If you play during the Rise of the Empire, then the Sith are nothing more than a dirty secret. A cult that the Jedi and the Republic need to stamp out before they summon forth some nasty ick that will swallow souls like nobody’s business.

If you play during the Rebellion Era: Well, kids, the Sith are in charge. And here you thought all those deaths on Alderan were to test out the new battle station.

Aside from starships and all that jazz, “Curse the Darkness” differs from normal Cthulhu games in terms of scope. No longer is humanity crawling around the surface of one world. Star Wars depicts a rather large interstellar civilization. There’s still much of the galaxy that is largely unexplored by Republic/Empire teams. (It’s likely quite explored by the natives, but we’ll leave that can of worms alone.)

The giant alien monstrosities and the horrors beyond space and time are a bit bigger, and a bit farther out. Instead of isolated villages and primeval forests, you now contend with backwater planets, and a wilderness of uncharted stars and planets. If your starship breaks down in the middle of space, then you can’t just walk to the nearest gas station to get help. No, even inside a solar system, you can be thousands of miles from any form of life, with nothing but vacuum to keep you company.


With the creation of a d20 Call of Cthulhu, it becomes easier to blend other games with the Mythos, especially those games using the d20 system. Like Star Wars.

The first thing that you’ll need to blend these two games is Sanity Points. Fortunately, you can just use d20 Cthulhu’s system and base Sanity Points off of the Wisdom attribute.

Next, the Mythos skill. My proposal for this is that you simply replace it with “Sith Lore”, and have it work the same. This means disallowing players the ability to buy Knowledge (Sith Lore) starting out. Otherwise it functions the same. Once you start bestowing ranks in it when encountering Sith stuff, you will likely tip your hand if you meant for it to be a secret. You may want to hide ranks in this if you’re being stealthy.

Also, while the normal Sanity loss for seeing dead bodies and other gruesome sights may be applicable, seeing strange non-human sentients isn’t that mind warping in the Star Wars universe. Otherwise Luke would have gone psycho after walking into the cantina in Episode IV. Also there’s the simple fact that not all the players will necessarily be human.

So, aside from the mundane horrors, I propose the following guidelines for Sanity loss.

  • Truly Bizarre Aliens: Talking fogs, extra-dimensional non-Euclidean messiahs (like in McIntyre’s The Crystal Star), and possibly hoojibs. Even then, I wouldn’t assign more than 1/1d2 or 1/1d3 for Sanity loss.
  • Creatures of the Dark Side: These would include not only mutated Sith monsters, but also Great Old Ones and their minions. So, Deep Ones, Byakhee, Serpent Men, etc.
  • The Dark Side: Any exposure to the Dark Side should cause Sanity loss. To be more precise: for each Dark Side Point you gain, you lose a Sanity point. Let’s hope you stay good.

Also, you may even want to allow spells from d20 Cthulhu to be used by those possessing Sith Sorcery. Only seems fair, if they’re going to be doing any bad summoning. If you’re feeling generous, you could create an equivalent feat called “Jedi Mysticism” for those who cling to the Light Side.

One tricky bit will be the conversion of Mythos monsters from the D&D style entries in d20 Cthulhu into Star Wars rules. Some items to keep in mind:

  • Wound Points are equivalent to a creature’s Constitution score. However, also remember that the exceptionally large and small creatures have a multiplier to this amount.
    • Dimunitive: x1/4
    • Tiny: x1/2
    • Huge: x2
    • Gargantuan: x4
    • Colossal: x8

    So this means that Cthulhu, with his Constitution of 29 and his Colossal size type would have 232 Wound Points.


  • Vitality Points work a lot like Hit Points in the way they are determined. If you’re feeling lazy, just give creatures Vitality Points equivalent to their Hit Points. No one will likely notice or care.

Adventure Ideas

That’s No Moon

It’s the height of the Empire, and the Emperor is about to unleash his most deadly weapon yet. In A New Hope, this would be the Death Star. In “Curse the Darkness”, though, it’s simply a moon-sized Dark Side monstrosity (complete with hanger bays, tractor beams, and crew quarters) that extends a proboscis down into a planet, and, utilizing the wrath of the Dark Side and absurd amounts of gravity manipulation and extra-dimensional space, crushes and sucks up the planetary mass. That’s all.

Tarkin and Vader test this out on Alderaan, horribly warping the fragile little mind of Leia.

The players will need to somehow stop this horrible fiend. A proton torpedo down a convenient exhaust vent likely won’t do the job. However, a rare Jedi artifact that they have to track down may do the deed quite nicely.

Traveling Through Hyperspace Ain’t Like Dusting Crops Kid

Warhammer 40K had one aspect in earlier versions (and may still have it in the newer incarnation) that still sticks out for me: traveling through the Warp (their equivalent of hyperspace), exposed you to dire, icky things and you ran the risk of somehow becoming altered, either in mind or body, by the Powers Beyond Space and Time

And here you thought your only hyperspace mishaps involved flying through a star.

Here are a few ways to handle this:

  • Heroes Horribly Mutated: In transit, the heroes get to make a Fortitude save to resist the change. Make it as hard as you like. Those failing first spend a week exhausted (in the d20 sense of the word) while their body slowly warps around them. At the end of things, they are horribly disfigured in someway. This could be oozing sores or a harelip. This could be that their head is now inset in their chest, they have four arms, their clothing has fused to their body, or they suddenly have an internal organ that sprouts Dark Side mutated wasps, making them into living hives. Each person will have a different horrible mutation. These could be almost beneficial. They could simply suck. Whatever game effects this has, you should at the very least have the following consistent:
    • The horrific nature of their appearance grants them a bonus to Intimidate checks. +1 to +4 depending on severity.
    • This is mostly untreatable. Small cosmetic things can likely be fixed, but having your head inset into your chest is a little beyond the scope of even Star Wars medicine. A powerful Jedi healer might be able to fix it. Maybe.
    • Drastic body changes could also make some skills, such as Treat Injury more difficult to use on these characters.
    • This is likely to cause drastic Sanity loss to both the victim and those watching the change.
  • NPC Passengers Are Changed: So, there are, traveling through hyperspace, when you pop out in the middle of nowhere because your Wookie co-pilot forgot to carry the two. Your hyperdrive is a twisted lump, it will take you months using your backup hyperdrive to get anywhere, and suddenly passengers start dying. One of the other passengers, or possibly a PC, has been driven horribly insane by something that touched their mind in hyperspace. And he has decided that everyone must die. You don’t know which one it is, you had better find out before they come to get you, and you are stuck in a small metal box floating through a whole lot of nothing.
  • PCs Are Horribly Twisted: If you are good at running good psychological horror, you could even use the previous scenario on all the PCs. The ship is effectively stranded in space, and everyone starts to hallucinate, suspect each other of wrong doing, etc. Hijinks ensue.

Begun the Clone War Has

So, Lucas wants us to believe that the purpose of the Clonetroopers is that they are simply cloned from genetically superior stock by long-necked rip-offs of grays, and given great training, so they can become super bad-asses. This of course is why their descendants, the stormtroopers, can’t hit anything with their guns, and are get thrown about in their shiny white armor by unarmored smugglers.


If we go with the notion in “Curse the Darkness” that Palpatine and Vader are agents of mind-bending evil, then we then face the problem of: How do they maintain a standing army without them going bugnuts from the mind warping horrors around them?

It’s quite possible that any of your favorite Mythos races assisted in the development. Mi-Go, the Great Race of Yith (or their agents in the Present Day), or even the Elder Things. Yes, those wacky Elder Things that brought you shoggoths could also be responsible for the Clonetroopers. No, Yoda, that’s not a very weak version of a Shoggoth Lord inside that shiny white armor.

This is No Cave

A common staple of the Mythos is that there are all sorts of winged things that fly through space. Cthulhu, Mi-Go, byahkee, the occasional Elder Thing. This takes on a whole different image when you put them in a star-spanning civilization and toss in hyperspace. And your players were worried about mynocks chewing on the power cables and the occasional space slug. Life gets suddenly very scary when a star-spawn of Cthulhu hides out in an asteroid field and decides your X-Wing looks might tasty, or an Elder Thing decides to give his three wings a rest and hitch a ride on the back of your ship.

The Supreme Chancellor Has Secretly Dispatched Two Jedi Knights

Let’s do a little dot-connecting. Palpatine is a Sith. Sith are in cahoots with our Mythos-style Dark Side. Palpatine is also from Naboo, a planet with a native amphibian population, and an extensive network of deep, underwater caves.

Your PCs are sent by the Supreme Chancellor to investigate this whole Trade Federation fiasco. Instead of helpful gungans, they run into small, isolated backwater communities of humans who look to have serious genetic defects, perhaps from inbreeding. In a different reality one would associate the look with Innsmouth.

Woe is he who tries to reach Theed through the planet core. Princess Amidala might be totally ignorant of the horrors beneath the waves. Maybe.

Yub Nub, Eee Chop Yub Nub

As a last item, keep in mind this heart warming thought: Azathoth is a churning horror at the center of the universe. In the Expanded Universe, Palpatine has a secret base near the center of the galaxy. What if the two bits of spatial real estate weren’t too far removed?

If there is sufficient interest, I can expand this further in later articles, providing conversions for monsters, rules for Mythos-style creature types, spells specific to the Star Wars universe, and so on. If interested, add a comment below.


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