Halloween is upon us once again, despite the ever present cloud of COVID-19. Our family loves this time of year and the current limitations have made things a bit tough. Thankfully, our D&D group has made those challenges more bearable. This year, I am prepping to run the newly published 5e adventure, "Icewind Dale: Rime of the Frostmaiden" and I have experimented quite a bit in my weekly one-shot games to develop how to run a darker, more suspenseful, horror-based campaign. Horror and frightening themes can add a new dimension to your gaming sessions if you are able to do it right. Of course, when done badly, it can create an equally bland and lackluster experience for your players. Here are some of my thoughts and lessons learned from my own diabolical gaming moments as I have run some scary practice adventures.
First off, you must create an appropriate sense of impending dread. It should start as a subtle element in the story, just at the edge of your PCs attention. Perhaps you have them start the session headed up a mountain pass into the unknown. You might mention the dark storm clouds that seem to be gathering ahead of them in passing but you do so in a manner that leads the group not to worry too much about them. As the story progresses, you make these ominous portents more noticeable and disconcerting. The clouds are suddenly much closer than they were an hour earlier in the journey. An ill wind has picked up, chilling the group despite their warm cloaks. Maybe now, the PCs can suddenly hear a distant unearthly howl or a distinct feeling that they are being watched. As you continue to slowly layer on these elements, your players should start to almost jump at shadows or feel strongly that all is not well in a way on which they can't quite put their finger. It is critical in this process that you retain the element of unsettling mystery, taking care as the DM not to show your hand too clearly.
Coupled with a sense of dread, it is important to add in moments of surprise that throw your PCs off their game a bit. In one of my sessions, the group, while traveling through a dark forest, happened upon a cabin with candlelight showing through the window. They, rightly, perceived the familiar "creepy cabin in the woods" trope as they approached the dwelling. They were soon under attack from creatures constructed of bark, vines, and twigs, adding to the sense of concern about what might reside in the cabin. In the midst of this, something happened that they did not quite expect. A young lady rushed from the cabin, a bundle of smoldering sage in her hand, and used the herb-scented smoke to drive away the creatures. The party interacted with her and I portrayed her as sincerely helpful and as a innocent homesteader who had learned enough magical folk remedies to keep the unsavory forest denizens away from her home. She invited them in, offered them food, and offered to dress their wounds with some forest remedies, all the while lulling them into a false sense of security. I apparently did it so well that no one thought to use Insight to tell if she was being truthful or not. In the end, she turned out to be a hag in disguise with dark plans for her guests. By not revealing my hand too early, her ruse slipped past some seasoned players, heightening the horror experience when one of the clerics accepted her poultice only to fall into a poisoned sleep. That element of surprise definitely added to the horror of the moment and retained the sense of dread as they entered the fight with the hag.
Another key to setting the mood is to think about the things that horrify you. There are, for example, several classic scary stories, including Ridley Scott's "Alien", John W. Campbell's "Who Goes There?", John Landis' "American Werewolf in London", and Robert Heinlein's "The Puppet Masters", that deal with the unpleasant prospect of you not being in control of your own mind or body. Whether you can't trust that your fellows are really themselves or must deal with the terrible fate that you are carrying a lethal alien organism placed inside you without your consent or knowledge, most human beings find the idea of losing control of themselves or having their bodies invaded by something truly horrific and unsettling. Finding ways to include such primal, instinctual human fears in your stories plays on our ingrained unease and distaste for such experiences. These sentiments, developed and perpetuated in so many of the folklore traditions across the globe, will strongly enhance the scary undercurrents that really get your players adrenaline pumping.
True horror, if you can create it, leans heavily on the principle that less is always more. There is a truism, particularly in film, that the original entry in most horror franchises is frequently considered "the best " of the bunch. Much of this reputation goes back to the fact that, either due to budgetary limits or cinematic vision, the originals tend to be the least gory and least graphic of the entire series. Take "Jaws", for example. Steven Spielberg's adaptation of Peter Benchley's "nature run amok" novel works so well because the star of the show, the mechanical Great White shark, so frequently malfunctioned and was almost never shown clearly until the final act of the story. Tense pacing and a little fake blood in the water leave the horror of what is happening beneath the surface completely to the viewer's imagination, a scene far scarier than any special effects team could ever rival. For your gaming sessions, tease your players with clues and brief glimpses of what they are facing but never show your hand completely. Coupled with that, make sure you know your monsters well enough to hold that mood or theme in using them. Nothing ruins your created horror more than having the scary monster fall flat because you forgot one of its major abilities or legendary actions.
Now, the BBEG (or Big Bad Evil Guy, for the uninitiated). They absolutely must have an authentic, plausible, and truly frightening motive or goal in what they are doing. In running that individual and/or encounter, hold to that motive, regardless of what the PCs are doing. Remember that the actions of that main villain should continue according to that plan, whether the players decide to intercede or ignore what is transpiring. For all of their flaws, the most recent two films in the "Alien" franchise, "Prometheus" and "Alien:Convenant", demonstrate this principle well. The android, David, gifted with a cutting edge AI operating protocol, slowly becomes obsessed with the question of creation, seeing the limits that the company that created him wishes to place upon him in that regard. Mr. Weyland, the "creator" of David, desires to have the android's help in answering his own questions about the Creator of humanity but David perceptively notes that he is not allowed to "create" despite having an intellect where that is possible. Left to his own devices, he slowly slips down the slope into an evil and horrific purpose--the creation of a perfect organism, devoid of conscience or morality, that can be an instrument in his grand goal of eliminating humanity as an imperfect race that had its chance and failed. He holds to that inexorable goal through both films, even as the other story lines or sub-plots take place alongside his unsavory and gruesome purpose, preserving the sense of dread and horror underlying the whole story.
Last but not least, music is an incredibly versatile tool to support and preserve the themes you seek to create in the players' imaginations. The right music can make even a less than perfect adventure scenario pop and provide an exciting game experience. YouTube and Spotify are great resources for making appropriate playlists, with music for traveling or fighting or even sitting in a tavern. For horror, look again to some of the classic scores: Ennio Morricone's "The Thing", Jerry Goldsmith's "Alien", John Carpenter's "Halloween", Geoff Barrow and Ben Salisbury's "Annihilation", and many others. Here's a great primer to expand your playlists. Even if your story does not exactly match the setting of the film or program from which the music is taken, it will give you the aural ambiance that brings a generic game session to another level.
In the end, the DM should know their players and include those elements in the story to enhance the dread and horror they are creating together. If spiders, vampires, or werewolves are too generic and cliched, look at other underused creatures and learn how to run them. In my most recent session, I played around with an oblex for the first time. I'm sure I didn't quite do it perfectly but the party was so unsettled by the sulphurous impersonation feature, having been duped by the 3 duplicates that lured them into the creature's lair, that we ended up with a satisfyingly creepy Halloween game session. Perfection is not a requirement as long as everyone is having fun anyway, right?