See P. XX: Bar the Gates!

See P. XX a column about roleplaying by Robin D. Laws

Buffy’s hometown had one. You fall into one when you open a Hellraiser cube. The Stranger Things gang can’t seem to stay out of them. Like any basic horror trope, the sinister portal to another world fits any GUMSHOE game that journeys into fear.

The default gate we think of in this context exists somewhere else, already halfway to hell: out in the woods, in a basement lab, in the attic of a haunted house.

Your sinister gate could flip the script by appearing in the middle of a busy city, unnoticed as such by thousands of passersby every day. An illusion, or our collective desire not to see that which should not be seen, masks it. Forms it could take include a metal gate across an alleyway, the steel sidewalk hatchway memorably seen in Russian Doll, or a bricked-over old door in the side of a wall that opens… under the right conditions.

The mythology of The Esoterrorists rules out a simple gate between our world and the Outer Dark. When its denizens can move easily into this world, it’s game over: the game’s big threat, the tearing of the membrane, has occurred, and the demon apocalypse has begun. For this game you’d have to adjust the gate trope into more of a pocket dimension. It exists as a metaphysical carve-out, a piece of this world operating under the physics of the other one. The Outer Dark Entity inhabiting it still had to through membrane-thinning summoning magic to create the pocket world behind the gate or door. It can’t leave the pocket dimension, and so has to lure people to step into it before it can corrupt, eat, or otherwise mess with them. To get rid of the creature, the agents must learn how to destroy the gate, sending it back to the Outer Dark. Or maybe getting rid of the creature in some other way causes the gate to disappear.

In Trail of Cthulhu, the gate could take investigators into a non-Euclidean space, the Dreamlands, another time, another planet, or some combination thereof. The pocket dimension might be a minor manifestation of Yog-Sothoth itself. The clues the investigators discover might describe it as an an avatar, spawn or virtual replica of the full deity. It might lure in victims to destroy them, or to mentally dominate them so they can go out into the world to do its bidding. In the indifferent manner of Mythos foes, a sapient dimension beyond the gate could simply exist as an anomaly, minding its own cosmic business, harming humankind by proximity without care or intention. The Colour Out of Space, but in gate form. In that version, scientists and curiosity seekers enter it out of their own tragic desire to understand what should not be understood and experience what should not be experienced. The investigators realize that it’s the flame, and the victims destroyed by it—who share their own mission and personal qualities—are the moths. To end the menace, they must learn more about it, which once again confronts them with the terrible central paradox of Mythos-busting: too little knowledge and they can’t act. Too much, and their minds crumble, and they can’t act.

In three out of four of the Yellow King Roleplaying Game sequences, an innocuous-looking gate seen from a city street could indeed act as a portal to Carcosa. Perhaps people have to have read the play, or at least gained some dread second-hand awareness of it, to perceive and enter it. Or maybe it just sits there, a warp in the world’s logic, for any Belle Epoque boulevardier, Continental War soldier, or curious gig-economy worker to stumble into.

In the Aftermath sequence, set in an alternate present after the fall of the totalitarian Castaigne regime, all gates between worlds have been blasted shut. Your gate can’t go to Carcosa. But it could have come about as a partially successful attempt by fugitive parageometrists to create one. Maybe it has taken on consciousness of its own and must feast on people to survive. Having already snacked on the regime experimenters, it now attracts others to devour. Or it appears as a hell the ex-insurgents’s revanchist enemies try to pull them into.

Alternately, in any sequence, the realm behind the gate might the intangible fortress of a reality-warping Carcosan entity. It’s a lair, not made of rock or drywall or debris, but of changes to the prevailing metaphysic. Like most beasties, it can leave its nest, but is safer and tougher when within its confines. This gives you a monster that can head out into the broader environment to take victims. The Difficulty Adjustment for the creature goes down outside the lair, and up within it.

Or the pocket realm could represent its vulnerability, a sort of battery of impossibility energy it relies on to survive. To banish it to Carcosa, or cause its disintegration, the team must destroy the micro-dimension while the creature is elsewhere.

You could adapt this last idea to The Esoterrorists or Trail just as easily.

Like any GUMSHOE menace, the sort of mystery you choose to weave around your gate helps determine how it works and the information the investigators must gather to overcome the threat. The obvious scenario premise: victims are disappearing into the gate, and the PCs must figure out what’s going on and destroy it. In a forgiving game, like a Fear Itself outing starring feisty kids, previous victims might still be found deep in the weird realm. In typical horror modes, they’ve been long since consumed. Success means preventing others from meeting their fate.

If the gate moves around from place to place, the investigators could uncover about the nature of the threat in an early scene. The mystery shifts from “what is this thing?” to “where will it show up next, so we can banish it?”

Human antagonists might have constructed or conjured the dimension to accomplish some wider goal. There the investigators have to identify them and stop them from realizing their plan.

Finally, a weird pocket realm could appear as a side element. A magician or parageometrist creates it as a trap to lure nosy parkers.

A pocket realm that moves from place to place could even appear as an Antagonist Reaction, waiting on the other side of any door or gate to ensnare the investigators.