Not just incomplete in the sense of “add players and a Dungeon Master”, but incomplete in the sense of “this adventure is missing important things I need to run it!”
Sadly, it’s our lot in life to have incomplete adventures. The fact is that there are three major things that stop adventures from being complete: space, time and imagination.
For professionally printed adventures, space is a huge consideration. There’s only so far you can shrink the font. At some point, you run out of words. So, you need to concentrate on what’s important. And thus, stuff you consider unimportant doesn’t make it. Even in electronic-only publications, you don’t want to include everything. Do you want to include the entire life history of every NPC? Likely not. It creates clutter and makes it harder for a Dungeon Master to find important information.
Likewise, did you want to release the adventure this year? Surely you can spend another year writing more material and polishing what’s there? Sadly, for most adventure writers, we’d rather like to see the adventure released in our lifetime. Adventure writing is a lot more time-consuming than you might expect – just ask Alphastream.
However, the primary problem is the imagination. A lot of times, the adventure’s writer didn’t imagine you’d need that information. The writer didn’t foresee the steps a group would take that would require that information to be relevant. This is one reason playtesting – and having good and numerous playtesters! – is so important. You discover the things you left out and the things you didn’t foresee.
Should the adventure designer try to foresee everything? Probably not. One of the reasons the game is so unique is that it allows the play to move beyond the written page. If you play a computer game or, showing my age, one of the old Fighting Fantasy game books, then you’re constrained by the decisions of the designer. You don’t have flexibility. The Dungeon Master can create new material to move beyond the printed adventure and react to the decisions of the players.
For me, the most problematic aspect of an adventure to write is the Non-Player Characters (NPCs). The Dungeon Master needs, in succinct form, a description of how to play the character and how they’ll react to the players. To do this well? It takes time and space. There isn’t one format that covers every use of NPCs, as they get used for many different roles in adventures. You have the quest-givers, the information sources, the henchmen, the villains, the bystanders, the merchants… The list goes on and on. I like to think that the core of an NPC is twofold: a set of goals and information they know. The first allows the DM to determine how they act; the second typically underlies their importance in the structure of the adventure: of providing a way for players to get to another encounter.
It’s when the structure of the adventure is incomplete or badly thought out that I run into the most problems. If I can’t see the linkages that take you from one encounter to another, how do I run it? Investigations are particularly prone to this, with the one vital bit of information being made so obscure that the players can’t see it! Oops!
The unusual thing about role-playing game adventures is that most, even if incomplete and missing vital portions, can still be used. You can use encounters, NPCs, traps, descriptions, and histories from one adventure in another, perhaps one you’ve designed yourself. Or you could run the incomplete adventure by filling in the missing bits with your inventions. We tend to call this “being a Good DM”.
I think we can all agree that, by the very nature of role-playing games, that every adventure must be incomplete and that the DM is going to have to fill in the blanks. However, there’s a difference between inventing extra details for an NPC because the players have taken more interest in them than expected and having to invent crucial details because they’re missing. Even between those two options, there is a wide range of circumstances. I get annoyed at Hoard of the Dragon Queen because it doesn’t name the cultists travelling with the caravan to Waterdeep or give them any personalities, but I’ve been able to run the adventure three times very successfully despite that – and I included a lot of interactions with said cultists.
As you get more experienced as a Dungeon Master, you’ll get better at covering for the “missing” bits of adventures. That’s part of the skills of the Compleat DM.
Unfortunately, most adventures don’t have a label on the outside indicating for what skill-level of Dungeon Master they’re designed. There are significant drawbacks in designing all adventures for brand-new DMs – just see the 4E HPE series of adventures. But Dungeon Mastering is such a complex art, with each DM having their own strengths and weaknesses, so how does the adventure designer know what missing information will cause problems? Playtest, see what the DMs say, and adjust. And keep listening after it’s released to learn from what people say.
Adventure design is an evolving art. It’s not an exact science, and different adventures require different styles of presentation. As a Dungeon Master, you get better by running games. As a writer, you get better by writing. And both writers and Dungeon Masters get better by paying attention to feedback: seeing what works and what doesn’t. Adventures may be incomplete, but that doesn’t mean they’re not enjoyable!