Designing a Cult's Hideout in Dungeons & Dragons
Cults, like any secretive organization, can hide out just about anywhere, be it in plain sight or far from prying eyes. But whether they’re based in a nondescript urban building or a foreboding ruined castle in the mountains, a cult’s hideout should be challenging to get into and full of dark secrets.
A small cult operating in a city should meet somewhere inconspicuous, like the basement of a business owned by a member. Such a cult could also find safety below the streets in the sewers or catacombs. The 2014 horror film As Above, So Below is a great place to look for inspiration for this type of cult hideout.
Beyond the city gates, you might find a cult underground in an abandoned mine, a natural cave complex, the ruins of a dwarven city, or any other type of underground network not currently occupied by other creatures. What better place to conduct foul and profane rites than in the depths of a dungeon?
A dungeon that has been recently cleared by the party would work nicely for this purpose, and it would have the added effect of demonstrating to your players that your world is a living, evolving place and that the players’ actions have tangible consequences. A dungeon recently cleared by the party wouldn’t stay empty for long, and any number of nefarious organizations might move in to fill the vacuum.
Cult lore might dictate (un)holy sites where sacrifices and other rituals are required to be carried out. These could be the site of an ancient battle, a secluded mountaintop, a haunted castle, a mysterious arrangement of stones, or that shining metallic structure leaking poison that is said to have fallen from the sky. Each of these locations suggests a different type of cult, as well.
Accessing the Hideout
Any hideout should have some way of keeping uninvited guests out. An object such as a particular coin or ring given to cult initiates might be enough to gain entry, either by using the token as a key to unlock a door or by showing it to a guardian. This would require the party to catch a glimpse of someone entering a building after displaying or using the object and then loot such an object from an unsuspecting cultist.
A cult might favor less mundane methods for controlling access to its hideout. The entrance could be behind a secret door, but nearby there is a visible door guarded by a glyph of warding spell (or symbol, if the cult is powerful enough). When an intruder attempts to open the decoy door, the spell is triggered. A more mischievous cult might place a magic mouth on the hideout’s entrance to give red herrings to intruders by speaking nonsensical riddles or by directing them to another location.
Cultists might gain access to the hideout by speaking a password, walking a particular path to the entrance (for example, counter-clockwise around the perimeter of the entryway), or inscribing a sigil known only to cult initiates on the door. Whatever you choose, flavor it to incorporate cult lore so that the players learn something about the cult in the process of gaining entry.
Alternately, it might not be a trap but an astronomical occurrence that opens the way: the door only opens when struck by the first light of dawn or moonlight from a full moon (or from a particular moon, if your setting has more than one).
Inside the Hideout
Once the players are inside, you can harass them with all sorts of simple and complex traps to keep them on their toes or reward them for doing their research before going in. Cultists might know the safest route through a labyrinth, but intruders might stumble into tripwires and down dead ends before finding the inner sanctum.
Furthermore, different parts of the hideout should only be accessible by certain members of the cult. Low-ranking initiates might be excluded from the reliquary, where powerful artifacts are stored, or from the sanctuary, where high-ranking members speak directly with their evil patron.
Similar to the reliquary and sanctuary, access to the archive, where their scriptures and records are stored, might also be restricted to high-ranking members. Areas open to all members would include training (or brainwashing) rooms, sleeping quarters, and dining halls. The random table for “Dungeon: Temple or Shrine” in Appendix A of the 5e Dungeon Master’s Guide can be applied to a cult’s hideout as well.
If the cult is particularly depraved or if the tone of the campaign is more horror than high fantasy, the hideout might also contain torture rooms. The nature of these chambers should provide clues as to the cult’s purpose: that torture rack is halfling-sized, leading players to conclude that this cult has a grudge against halflings.
A hideout may not have been built by the people currently using it, but they will undoubtedly leave their mark on the place. What are some locations you've used for a cult hideout? How did the cult make it their own?