“The bridge is protected by an ancient trap,” declares Xenk the Paladin (played by Regé-Jean Page) in Dungeons & Dragons: Honor Among Thieves. “We must not trigger the mechanism.” Of course, the trap is immediately triggered by Simon the Sorcerer (played by Justice Smith) causing the bridge to crumble before them. The irreverent humor of the moment and the all-too familiar “oops” moment makes the movie feel like a game at the table, especially because traps can be found anywhere and are a staple of any dungeon crawl.

In Dungeons & Dragons, traps fall into two categories: mechanical and magical. The mechanical variety can be a simple one and done like a snare or pit trap. Once triggered or disabled, it poses no imminent danger. Conversely, they can be complex like stepping on a pressure plate and unleashing a series of terrible and ongoing dangers that must be disabled in stages once triggered. Think whirling blades while a chamber fills with water. A magical trap can be as simple as a glyph of warding or as complex as teleporting characters into a dangerous situation where they are also subjected to spell or mechanical effects. The combinations are almost endless.

A well-designed trap is one that takes characters by surprise. Sometimes it means distracting the characters with something of interest (whether it’s possible treasure or a suspicious looking cobblestone), so they don’t focus on the real trap. The Dungeon Master Guide gives a good introduction to traps in Ch. 5: Adventure Environments (see: “Traps”) and Xanathar’s Guide to Everything takes traps to the next level in Ch 2: Dungeon Master's Tools (see: “Traps Revisited”). Both of these source books provide examples as well as guidelines for creating your own traps, but you can also find classic traps sprinkled throughout Tales from the Yawning Portal.

What makes a good trap? For that we need to look at the elements of trap design. Let’s break it down into two phases: the first is detect, trigger, and disable; the second is damage, saving throws, and lasting effects. Every step in these phases should give players a chance to overcome a trap in a different way. It’s what makes a trap both fun and interactive.

Every trap has a trigger, the thing that causes a “rocks fall, everyone dies” situation. Before that though, there is an opportunity to find and circumvent the trigger. Characters can do this by using their Investigation or Perception skills. Alternatively, a character could cast the find traps spell. Once discovered, they then can disable the trap using specific ability checks or magic. For example, to disable a trapped lock, a DM might ask for a sleight of hand check and give advantage if a character has proficiency in this ability or with thieves’ tools. Depending on the trap, casting dispel magic could do the trick also. Failure to disarm a trap results in triggering the effects. This is where saving throws are made, damage is dealt, and characters learn about any lasting consequences of failure. For complex traps, the danger increases every round and multiple elements must be disabled to render the trap inert. When it comes to consequences, there are three danger levels (each pretty self-explanatory): setback, dangerous, or deadly.

When placing a trap, there should be a rationale behind its existence — the trap’s raison d'être — unless you’re designing for the archlich Acererak who has taken a hobby interest and turned it into a full-time job. Whether it’s a long-forgotten trap from a ruin that’s been grown over by nature or something made to keep an artifact from falling into the wrong hands, all traps are created by an individual to serve a purpose.

What about puzzles, you may be asking? In the Honor Among Thieves trailer, Xenk opens what looks like a puzzle box to withdraw a helm. Puzzles require logic to solve and the paladin likely had to make some ability checks to claim that treasure. If you want to learn more about them, you’ll also find puzzles in Tasha’s Cauldron of Everything in Ch. 4: Dungeon Master's Tools (see: “Puzzles”). The fail-state for a puzzle could just be that it remains unsolved, but a wrong answer could bring on a “you chose poorly” consequence. 

Either way, traps are different from puzzles though there can be a bit of an intersection between the two. Essentially, puzzles exist to be solved and traps are meant to be avoided (don’t let Acererak tell you otherwise).