If you’ve delved in enough dungeons, you’ve likely had a close encounter with the dungeon Roomba known as the gelatinous cube. Classified as an ooze, this creature thrives in dark places such as ancient ruins and underground mazes. While many of the monsters that have appeared in Dungeons & Dragons over the years have origins in world mythologies, the gelatinous cube was an original invention of Gary Gygax. It first appeared in the original Dungeons & Dragons "white box" set (1974) in the Monsters & Treasure book.

Although they are transparent in nature and creatures inside the cube can be seen, their oozy form also gives total cover. This fact might explain why the characters in Dungeons & Dragons: Honor Among Thieves movie trailer took their chances and dove in to one. From the early teasers, it was clear that the film was supposed to feel like any game at the table where players sometimes concoct very hairbrained plans. In this case, they risked being engulfed to escape a slightly more dangerous situation with a displacer beast. Maybe one of the characters has acid resistance or a magic item like a necklace of adaptation that allows them to breath in any environment. A combination of these things would allow them to help the rest of the party move through to the other side. Otherwise, what awaits them in the area is a slow death of suffocating while being burned by acid.

For those who want to recreate this movie moment, there’s both a 6-inch-scale collectible gelatinous cube from Hasbro’s D&D Golden Archive that’s compatible with their figure lineup, or a cuter interactive plush from WizKids and KidRobot with accessories to pose inside. The meme factor has been strong with this special ooze. At SDCC 2022 there was even a special photo op “I Survived the Gelatinous Cube” and artist Lauren Walsh has found overnight success with the adorable sensation known as Woubble.

But what is the deal with these animated Jell-O blobs? According to legend, they actually have pretty dark origins as the spawn of Juiblex, the demon lord of slime and ooze. As you might imagine though, a gelatinous cube is not exactly intelligent enough to actively carry out evil plans. They’re more likely lured into service. Villains and ne’er-do-wells trap these creatures in places where they don’t want adventuring parties to go, all while cleaning up any bodies that might otherwise cause a dungeon to fail a health inspection. Their ooze nature allows them to get into all the little nooks and crannies for a deep clean of organic matter.

When it comes to gelatinous cubes of note in D&D lore, Glabbagool stands out. When Juiblex arrived in the Underdark, Glabbagool was somehow granted sentience. Found in the Oozing Temple featured in Out of the Abyss, this gelatinous cube is the very embodiment of the little ooze that could. It has pacificist tendencies and avoids fighting or harming others unless it acting out of self-defense, and has a genuine curiosity about the world and characters that populate it. If an adventuring party wins its trust, Glabbagool even could even offer to travel with PCs or gift them a magical mace located within its oozing form. Since Honor Among Thieves does have scenes in the Underdark, there’s always the possibility that the gelatinous cube featured in the trailer is, in fact, Glabbagool.

Befriending a gelatinous cube in your game is otherwise likely a one-sided relationship. It could certainly come in handy for a “leave no trace” group of ecologically minded adventurers but with a movement speed of 15 feet, it brings new meaning to the concept of slow living, or adventuring.

If you’re a DM who wants to add a gelatinous cube to a game, here are some simple tips. Since their Intelligence is so low, there is no tactical planning involved. As noted above, some villainous types lure these unwitting creatures to do their bidding. For instance, leading a gelatinous cube to the bottom of a pit means voilà — a self-cleaning pit trap. An unsuspecting adventuring could slide down a trap door. Once suspended inside the cube, other party members need to get creative in saving their party member since the cube is contained by the floor and walls of the pit leaving only the top area exposed for any kind of exit. Alternatively, put a gelatinous cube in dimly lit areas that are closed off or have “keep out zones” like with any good Roomba type cleaner. These zones can be contained magic or fire to keep the gelatinous cube from straying out of an area. There are also other environments to consider, like behind a waterfall.

Keep in mind that this creature has blindsight, meaning it can sense vibrations and move toward them. The creepy thing about all oozes is their pseudopods. You can imagine this large, transparent cube slowly moving through a dungeon with little filaments touching every surface to suck up whatever organic matter it can consume. When it senses prey, it can take a dash action to get up close before reaching out its pseudopods and attempting to engulf its next meal. Since a gelatinous cube doesn’t require sleep, it makes for an excellent addition to the right location since it’s constantly pulling a double shift as both oozy assassin and dungeon custodian.