Looking Over Book of Challenges: Fool Me Once
A vertical shaft has some traps to foil attempts at ascending it with magic.
The dispel magic trap is a clever bit of design, since it acts as a warning that may be further traps aimed to foil magic while still providing a chance to resist the effect and being unlikely to cause instant death if it works.
The advice for scaling up the challenge by putting enemies at the top of the shaft who can launch projectiles while standing within the antimagic field is nice and spicy.
For systems where the caster’s level affects the chance to dispel magic, either the GM needs justification for why a near-godly wizard set the first trap or the caster’s level needs to be adjusted.
I’m a strong believer in interactivity being important for good trap design, so I’d be open to deviating from the rules for glyph of warding (such as allowing more ways of figuring out their effects than just casting read magic and passing a skill check) even if I were running 3E or its descendants.
The boxed text is pretty worthless, and displaying self-awareness of how worthless it is doesn’t actually make it better.
While this may be the shortest entry in the entire book (less than 1 page in total length, including the map), it’s actually remarkable well-designed. The set-up is sensible, the first part foreshadows the real danger, and the whole thing is modular enough that it ought to have little difficulty fitting into any location where it’d be plausible. Sure, it lacks the adventure-defining potential of encounters like A Familiar Situation or Watery Grave, but that might make it a better fit for this book’s stated purpose (encounters that can be plugged into a dungeon with little preparation or introduction). It can even serve as a basic template for other magical traps, by either the GM or the players alike.
All in all, this is a very good example of how to make something simple, nasty, and reasonable. Its only downside is the amount of vertical space it requires, making it tricky to use outside of dungeons, towers, or the like.