Looking Over Book of Challenges: Dark Water Trap
An area of magical darkness hides other hazards.
Taking advantage of duergar being short by giving them confined spaces and low walls for cover is nice. It does render their enlarge ability somewhat counterproductive, but that shouldn’t be a major loss.
The duergars’ tactics in case they’re engaged in melee are basic, but spelling them out isn’t the worst use of space.
The scaling idea to add an electricity-based trap at the end of an encounter which could leave the party wet is a good reminder that multiple traps in a single encounter can take advantage of each other’s effects.
Jumping through hoops to satisfy the fetishized rigor of 3E feels like such a waste of effort, and there’s even an argument to be made that everything put together in this encounter still doesn’t block normal vision. Just pick a simple way to have some length of the tunnel be cloaked in impenetrable darkness or similar visual impairment and be done with it.
I can’t imagine a good reason why the lever to operate the walkway should require a check to throw it.
Presumably, the hatches to fill and drain the pit have been rusted shut longer than the orc remains have been in there. Given that all of the flesh has sloughed off of the bones and liquefied, that means the water has been sitting there long enough for evaporation to start taking effect. To cut a long story short, the hatches are one of those details that doesn’t so much explain something as it does call attention to how it shifts the question.
How exactly does a Disable Device skill check do anything to an open pit?
Firing blindly into darkness of a tunnel that forces travelers into a vulnerable position just because you heard a noise is asking for friendly fire incidents. In other words, the duergars’ opening tactics are bad unless there’s greater context to justify them expecting only hostiles to come through the tunnel.
Why exactly is the door to the resting chamber a secret door? That seems like a pointless hassle.
As a stand-alone encounter, I’m not too fond of this one, but it can work. I’d add some extra enemies so that they could have a rotation of people sleeping/foraging/guarding, but the basic set-up of a shelter in a dead-end with a defensible approach is fine.
Where I like this more is as a security chokepoint in a larger installation. Make it part of a critical pathway instead of a dead-end, and it becomes a fairly simple way to pose a major challenge just through the combination of a few things that wouldn’t be nearly so interesting on their own.
All in all, this is a nice encounter to showcase how important vision and fortification are for influencing tactics. It doesn’t have anything that stands out and demands it be used, but it’s flexible enough to fit into many situations with a little rework.