Generic Adventure Module: The Big Dumb Object

by Allen Stroud

Generic Adventure Module: The Big Dumb Object
March 7, 2020 Allen Stroud

In this issue we continue our Generic Adventure Module series. These articles cover a particular plot you could introduce into your roleplaying game to run alongside your main campaign, or kickstart a new series of adventures.

The structures of these plots may also be useful to aspiring writers looking to put together a short story or novel. Where possible, we will try to keep the setting of the adventure as portable as possible.

This month’s adventure module is: The Big Dumb Object.

The Big Dumb Object (BDO) is a science fiction trope that has been lurking around since the 1970s, but the term was originally coined by reviewer Roz Kaveney in 1993’s The Encyclopaedia of Science Fiction. Arguably, the term was derived from the titular element of Larry Niven’s novel Ringworld (1970) — the Ringworld itself, a 186-million-mile artificial habitat constructed around a sun.

We could go back further. The legendary Flying Dutchman, a ghostly merchant sea vessel of the 18th century that sails the seas with no crew, has many of the attributes of a BDO; but stories about it focus on sightings, not of boarding the vessel and finding out the truth.

In current writing, a Big Dumb Object is usually an alien artefact of vast size that has been introduced into a conventional setting that the audience is already familiar with. The qualities of the BDO are such that it demands the attention of the principal characters in the story and so it becomes a major part of the plot.

BDOs are also a classic feature of some Arthur C. Clarke novels. Rendezvous with Rama (1973) is an excellent exploration story. Read it, and make comparisons with the ideas of Niven and stories like At the Mountains of Madness (1931) by H. P. Lovecraft. But Clarke is doing something different to both of them: he has turned the environment (the huge alien spaceship named ‘Rama’ by the humans who are about to explore it) into a character. This trick by Clarke polished the trope and made it part of the science fiction writer’s toolkit. 

BDOs transfer well into films, providing a canvas and setting for a plot. They allow characters to discover things, experiment with them, and play out the consequences.

BDOs done well often aren’t that dumb. Recent films Annihilation (2018) and Arrival (2016) hint at an otherworldly agenda behind the alien presence. If the writer wants, some of that agenda can be the way in which human characters are reading into their experience — mapping their own ideas onto the vast alien presence, which might be confirmed as the plot develops. Either way, the hint of a purpose behind the BDO’s presence and its actions serves to maintain an element of tension in the story.

Roleplaying games and BDOs

If you decide to introduce a BDO into your roleplaying game, then the element of mystery is of paramount importance.

Despite being the most common use of this trope in novels and movies, a BDO doesn’t need to be an alien spaceship. It can easily become a mysteriously-appearing haunted house or a supernatural carnival, like the one in Ray Bradbury’s Something Wicked This Way Comes (1962). Fantasy uses are often static, requiring the player characters to travel to a location, but they absolutely do not need to be. Howl’s Moving Castle (1986) by Diana Wynne Jones is a good example of this, with its TARDIS-like properties, or Ready Player One’s Oasis.

The trick is to ensure the player characters have a reason to care about the device and a need to explore it. That could be to learn its secrets or to remove a threat from the planet or kingdom.


The exploration quest

Many BDO quests are unlike other quest narratives because the environment is often inside the BDO. That means that, as the gamesmaster (GM), the rules of the setting are yours to play with. Once the player characters are inside, you can devise all sorts of obstacles, traps, and puzzles for them to contend with.

The focus of a BDO quest is usually one of knowledge, even if there is a specific stated goal. The knowledge might be the stated goal — understanding how the BDO works and finding its control room, for example.

The key to keeping this  journey developing towards its goal is to ensure the rules of the BDO remain consistent and rational. Once the player characters start to figure out the how and why of things, the focus of the adventure shifts towards their next steps. In some respects, it can be worth allowing the initial obstacles to become assets as they move on.


Saravay’s Sinister Sanctum appears in the graveyard of Argantos City every 25 years. It remains for only a single night. Legend has it that the city’s lost treasure is hidden somewhere within the building.

The player characters are inside the entrance chamber and find a door at the back. It is locked. After deciphering some mirrored writing on the walls, the player characters are able to locate a key, hidden underneath one of the flagstones on the floor. They open the door and pass through, into a chamber with multiple exits.

A few moments later, there is a noise in the entrance chamber. A huge creature forms out of the air and begins to make its way to the door. Acting decisively, one of the player characters shuts the door and locks it.


In this scenario, the GM and the player characters have achieved a number of things. Firstly, the player characters have solved the puzzle of the first room. This will prime them for similar challenges, so expect them to go looking for mirror writing whenever they see messages carved onto walls!

Secondly, the player characters have a key. This key could be useful for only one door or it could open and lock many different doors. In fantasy, the key may have magical properties to enable this; in science fiction, it could be a pass card of some kind; in horror, it could be the rotten eyeball of the former owner of the haunted house… And so on. Whenever you provide the player characters with a tool, expect them to use it.

The GM has achieved other things. To start with, the player characters are now inside the BDO and unlikely to risk leaving, unless they encounter something worse than the creature they saw through the doorway. The obstacle placed there should counter some of the doubts they may have had about accepting the mission. As things stand, they seem to have no choice.

Additionally, the GM now has a measure on the ability of the group to solve problems. The nature of an adventure like this may require people working together and using their brains. By beginning with a fairly simple opening scenario, the GM can see how much challenge the group is interested in and capable of.

Finally, the player characters’ ability to communicate with the outside world is severed, or at least made much more difficult.

This kind of opening dilemma can easily be transitioned into other genres. Gaining access to the derelict spaceship’s airlock could be the dilemma, and — once achieved — the ship’s internal sensors detect the presence of life onboard, activating the shields and cutting off the player characters’ communication with their own spaceship.

Puzzles, obstacles, and traps

Exploration of a BDO can work in a similar way to any other dungeon-style adventure, but it can be useful to provide clues towards the knowledge you know the player characters are seeking. These might come in many forms:

  • a gradual collection of glyphs or symbols, 
  • fragments of a data transmission, 
  • fragments of the house owner’s journal, or 
  • pass codes held by dead enemies could be accumulated along the way. 

Knowledge of the BDO should be built up with each successful transition, so player characters feel like every element could be necessary. In many ways the roleplaying game application of a BDO has more in common with the setting of a video game, although it is best to hide as much game-like language from the narration as possible. 

It is important to vary your encounters. Player character will seek to use whatever tools they are given and will probably try the same tactics that worked in a previous situation before engaging their brains, so switch things up to keep them on their toes.


Time limits and rival teams

If you want to push the pace and keep the player characters on their toes, introducing a countdown of some kind can help. Perhaps the BDO is in someway unstable, or there is a time window before it leaves? Whatever the action that the player characters are trying to prevent, it will need a consequence. That consequence can even just be the fact that they will be trapped inside.

Time limits can be flexible when your environment is a BDO. Remember, you control the rules inside the object, so a little time manipulation is fine — so long as your setting permits it. Your rules should have a rationale and some consistency.

Alternatively, you can push the pace by introducing a rival. If a BDO is rumoured to contain a prize, then there are bound to be others who are up for the challenge of trying to learn its secrets. The best rivals are always one step behind the player characters. At times, they may even become the obstacle, with both teams vying for something to get them through the next situation. They can also be forced into working together, only to renew their rivalry afterwards. This can provide an interesting way to introduce non-player characters and set up a future encounter, involving a betrayal or another scenario in which the teams are forced to interact.

The mastermind

Eventually, the cryptic twists, trials and turns of the adventure will lead the player characters to some form of final confrontation. In fantasy, this is often the ‘boss’ monster encounter with a suitably-powerful enemy that stands in the way of the final reward. In this respect, the final encounter can become similar to a dungeon-based adventure.

However, BDOs offer the GM something different to use for their finale. As exploring the BDO to find out how it works is usually part of the goal of the quest, the opportunity to utilise the power of the BDO — and indeed, who should use the BDO — can be part of this conclusion.

Films like Indiana Jones and the Last Crusade (1989), or Pirates of the Caribbean: On Stranger Tides (2011) both involve the object of the quest (and its use) in the final act. These are not, strictly speaking, BDOs, but they set up a dilemma of power and of whom shall be given the right to execute it.

If your BDO plot involves the player characters working for an external agency — the United Nations, say — in their mission to board the alien spaceship and take control of it before it crashes into Earth, they might find the agenda of their paymasters is not as pure as they first thought. Or, when they reach the control room, they may find that the ship is not actually doing what they thought it was doing. Or, they may find both of these things are true and that the ship can be signed over to whoever they give the secret special code to — meaning that only one person can ever truly control it. 

The list goes on. There are hundreds of possibilities!

One under-utilised idea is to require someone to take over the ship and effectively sacrifice their character. The reward for this might be incredible temporary power in the story, but something that requires the player to accept that their character is going to become a non-playing character from now on. The focus then becomes on how the player characters determine who amongst them gets this; or indeed, if they have a non-player character with them who can do it. This could be solved through discussion, or even a fight breaking out.

We call this a ‘bauble plot’ — introducing a shiny bauble into a group that has powerful gifts for whoever can control it, and letting the individuals try to work out who gets it. The gifts can be the same or different for each individual involved.

Again, the elements that have already been established earlier in the story can become useful tools in this final scenario. A rival team might provide extra conflict, or a suitable person to be sacrificed. A time limit might rack up the tension, forcing people to make a choice. The BDO itself may intervene, deciding who the best person for the job is based on how they have acted whilst on the adventure.

It is also worth thinking about how granting power to a player character can affect roleplaying games.

At the end of Harry Potter and the Deathly Hallows: Part 2 (2011), Harry Potter breaks the Elder Wand rather than keeping it. This is a rejection of its power and signals the end of his story. In an equivalent roleplaying game module, I doubt that most player characters would do the same, as the player would likely see the wand as a just reward for their efforts and think about how useful it could be in future campaigns.

Whatever is determined, the game lever offered by ownership or the power of the BDO needs to be significant but fleeting. If it isn’t, you are granting whoever obtains it the ability to overpower any future roleplaying campaigns you might write and run in the same setting. Planning out this power at the beginning is a good idea and keeping the extent of it within the boundaries of the scenario you have planned should enable you to maintain a balance to your campaign.


An ongoing mystery

In a BDO campaign, the enigmatic nature of the object itself should ideally be preserved — even to the end. Whilst the player characters may have solved the puzzles they were presented with, good BDOs still have cavernous depths. Once the player characters leave, perhaps the BDO disappears, only to reappear again — this time with a whole new set of challenges?


Over to you…

Hopefully, this selection of ideas has got your imagination working. On the Parallel Worlds website you’ll find a sample BDO adventure module written with this structure in mind. Feel free to download it and adapt it to the system and setting you’re playing with.