There is a long tradition of funhouse dungeons in D&D and its descendant games. Gary Gygax favored large subterranean systems many levels deep, with the idea that each level was appropriate to adventurers of that level. Under him, TSR published several adventures, such as White Plume Mountain and Tomb of Horrors that were fairly nonsensical funhouses of peril.

Today, funhouse dungeons are out of favor–including with me–but that doesn’t mean you shouldn’t use them at all. Here are several ways to justify a bonkers dungeon.

1. It was Built by an Insane Person

I like to say that casting any high-level spell has a small chance of costing the caster 1 point of wisdom permanently. While it’s possible to recover it, this can sometimes lead to a downward spiral of an eccentric wizard foolishly choosing to cast more high-level spells, thus becoming weirder and weirder until he or she is certifiably bonkers. And bonkers wizards can use high-level spells to make bonkers dungeons.

This can happen to clerics as well, but since they rely on wisdom as their primary stat, they start with more and have more contacts that can help them recover.

Of course, you don’t have to be a spellcaster to be bonkers. You can merely be rich and powerful, and people will build whatever you want them to build.

2. It was Meant to Confound Evil Spirits

There are a remarkable number of traditions we practice to this day that are based on superstitions about confusing evil spirits. Having groomsmen and bridesmaids at a wedding, for example, was meant as a way to keep evil spirits from finding the bride and groom.

But in a fantasy world, the need to confuse evil spirits may be very real. Fiends from other planes may stalk the recently deceased or they may be trying to collect on a Faustian bargain the dungeon-creator made in life. But there may be rules about making it “fair” for the fiends by presenting traps that can be defeated and puzzles that have proper answers.

3. It was Meant to Confound Looters

Never mind evil spirits, there are very real tomb-raiders and temple-robbers who need to be stopped. Of course, if no one is ever meant to get at a tomb, it can merely be hidden and sealed–filled in completely, in fact.

But there may be reasons in certain cultures why loved ones, worshipers, or priests would need access to the tomb in perpetuity, and so making the path tricky would be a good way to discourage the casual looter while those who know the way and the solutions to the challenges are still able to pass.

If it’s a mausoleum, loved ones would want to be able to lay additional loved ones to rest as they died. If the deceased was worshiped as a living god, he or she may intend to continue to be worshiped and therefore have the tomb allow access to the faithful who have the correct passwords, puzzle solutions, and awareness of traps.

4. Those Inside May Need to Come & Go

In some cases, the creator may intend to rise again and leave their tomb, either to live a new life or to prey upon the innocent. So the tomb must allow the builder to come and go while avoiding traps and bypassing puzzles. A lich, for example, will intend to re-spawn from a phylactery if its body is destroyed, so it needs to keep the phylacteries in a safe location that it can still get out of.

Or the creator could mean for perpetual servants or worshipers to come and go, using the facility for worship and forever maintaining traps and resetting puzzles. Imagine the humble faithful stripping an adventurer’s corpse of valuables, adding them to the vault, and resetting the trap the killed the pitiful fool.

If it’s a monastery or hermitage, the inhabitants may be people who don’t want to be disturbed, and so only those given the passwords and warned about tricks can enter easily.

5. It was Meant to Be a Challenge

Depending on the culture–or the sanity of the builder–the place may be deliberately difficult to penetrate as a challenge to those bold and intelligent enough to navigate it. The reward may be the builder’s treasure or access to an underground city or some other reward.

These may be the trickiest of all, since the puzzles and traps don’t have to make a lot of sense: they are challenges for the sake of challenge. Reaching the vault may be congratulated by the builder, even if it was meant for people the builder knew (heirs, followers of the same faith, etc.) rather than adventurers.

But the intended challengees could be the heroes themselves. They could be given a quest/pilgrimage to visit the tomb of their order’s founder. They’ll have to solve puzzles and avoid traps to reach the sepulcher and perform a ceremony of honor before leaving and resetting everything. Then they get a divine reward.

Okay, But How is This Intact?

In addition to wanting to justify the existence of a funhouse dungeon, you may be bothered by the pesky question of how the creatures in it survive. In the early days of D&D, adventurers might open a door to a 20×20 room to find a basilisk somehow lives there.

Of course, any particular dungeon may be a combination of the ideas below.

It’s Maintained by Guardians

If at least one person comes and goes, that person can reset traps and puzzles. For some types of monsters, the guardian can also feed and care for them as pets/guards.

The guardian can be someone who lives in the dungeon or an outsider entrusted with the duty to check on it and reset traps and puzzles.

The heroes could be tasked with going into a hidden tomb of their own faith to reset the traps and puzzles that protect the resting place of their order’s founder from looters, perhaps as part to a pilgrimage challenge (type 5 above).

It’s Maintained by Magic

Powerful magic can periodically reset traps and puzzles. But it can also keep monsters in stasis until they’re needed to challenge adventurers.

Such magic can be arcane or divine, with divine magic being the more powerful and permanent, since a god or other divine being can keep watch over such a place.

It’s Maintained by Spirits or Undead

Essential spirits and ghosts of the dead can manifest physically to reset most traps and puzzles, if motivated by a duty. The spirits themselves can also be challenges. Likewise, skeletons, zombies, and mummies can act as both trap reset workers and guardians.

Constructs, such as stone golems, can likewise be animated to act as keepers of the tomb or temple.

It Doesn’t Need to be Maintained

Depending on the types of challenges you put in the dungeon, the traps and puzzles may not even need to be maintained. A tilting floor trap may just drop back into place. A puzzle solved may scatter its pieces by the mechanical action of the the adventurers opening the door it protects.

No one needs to feed or muck out the pen of a gelatinous cube; in fact, that monster is nature’s own vacuum cleaner, clearing up adventurer corpses as it sweeps corridors. The place may be a whole ecosystem or series of mini-ecosystems of creatures that live off molds and fungi, monsters that live off those creatures and molds and fungi that live off the waste of both.