Corridors of the Cube

It seems like a safe bet the Gelatinous Cube will not be winning the current Eleven Foot Poll, so I'm going to go ahead and talk about it in the context of my favourite encounter in Keep on the Shadowfell, the Corridors of the Cube.

Ten foot square corridors are a staple of D&D. I love them dearly, but they don't make the slightest bit of sense. After all, excavation is hard, expensive work. It is not cost effective to make tunnels any wider or higher than they absolutely have to be.

Here in what is ostensibly a military keep you might have expected cramped passages, maybe four foot across, only just wide enough for two people to move quickly in opposite directions - but no, the builders have decided what is good enough for Gygax is good enough for them. You see it, too, in dwarven architecture, where the stubby little diggers have allowed themselves enough headroom to give each other piggy-back rides. Hell, the corridor in my house is only three feet wide, and it seems to get the job done.

One of the things I love about D&D is that these kind of mechanical cliches are not just prevalent, but so prevalent that entire ecologies have grown around them. In the Corridors of the Cube we encounter the Gelatinous Cube, a transparent ooze in the precise shape of the corridor. It is a ten foot invisible cube, with its edges exactly scraping the corridor walls.

Let's point out this isn't just a monster specifically evolved to live within a standard RPG dungeon. It's a creature specfically evolved to hunt adventurers in an RPG dungeon. One of the Cube's biggest advantages is its transparency. You can see right through it, which means that, like a particularly fine spiderweb, you can not even notice it's there until you've already walked into it.

That only works on humanoids. Creatures with heightened hearing - like, say, anything naturally living underground - won't be fooled by transparency, and will hear it coming a mile away. Anything that can see in the infra-red will notice its distinctive heat signature. It's only humanoids, with their reliance on traditional light sources and edge-recognition, who'll fall prey to its camouflage.

In Corridors of the Cube, we find the Cube in its natural habitat. Players enter from the north and then have the choice of heading east or west. The Cube waits in its alcove to the east, and won't be detected unless players specifically walk into that space. Once players have picked an end of the corridor to walk to, the Cube emerges and gets between them and the exit.

If they've gone east, the Cube will take a leisurely ooze down the corridor and engulf the players at its leisure. Once engulfed, players take 10 ongoing acid damage and become dazed, and have to make an escape check (Acrobatics vs Reflex or Athletics vs Fortitude) to get out. It can engulf multiple players on a single turn, and characters who escape end up back next to the Cube with their turn used up, so actually getting away from the thing is next to impossible.

If players go west, they're in for even more problems. The room to the southwest holds two Corruption Corpses, a disgusting kind of zombie that throws pieces of its own flesh from range and deals aura damage to anyone who gets close. The Cube will literally drive the players into the corpses, until they're taking the zombies' aura damage even while engulfed.

When players eventually triumph over Cube and Corpses, they get the chance to ransack the room to the east of the zombies. Here they find a collection of children's toys belonging to Ceinwein and Drystan Keegan. Reading between the lines, it's not hard to draw the conclusion that the two zombies outside are intended to be the resurrected bodies of Sir Keegan's murdered children, which potentially makes for a poignant, yet disturbing, moment.

Alternatively, if you're not keen on your players beating up child zombies, a second possibility is that the children still rest in their graves, and the zombies are the knights set to guard over their corpses. Although one has to again wonder where Sir Keegan found time to build coffins and set guards during his busy schedule of slaughtering every man, woman and child in the keep and then killing himself.

This is a nearly perfect encounter. It's mechanically sound, it's tactically interesting, it's clearly explained, it surprises the players without being unfair, it ties in to the backstory, and there's worthwhile treasure at the end of it in the form of a safewing amulet +1.

Questions:

[1] Where did the Cube come from? The door into the area has been hastily boarded up and marked "Closed", but it's unclear whether this is hobgoblin work or an act of the keep's original inhabitants. The ecology of the Gelatinous Cube is something that does not bear much scrutiny.