In Kay's article, she points out there are 5 reasons to build a trap: capture, delay, frighten, kill and something she calls "the Trail of Worth." I agree with 4 of the 5. Kay doesn't explain what a "Trail of Worth" trap is.
Using Kay's classifications, let's revisit the Tomb of Horrors.
How do you classify the pit traps? They could be any of the choices. Realistically (beacuse of character level), they are delay traps.
The Green Devil Face is obviously a kill trap.
The Arch of Mist is a delay trap.
The 3 (4) Armed Statue doesn't really fit with any of the criteria. As I mentioned in Pt 2, I consider this a puzzle. But, it also acts as a trap, It eats resources. (I will touch more on this in a bit.)
The Magic Archway is a delay trap and also extracts a heavy resource toll.
The False Doors in the Great Hall of Spheres act to both delay and kill (?)
The chest traps are kill traps.
Rarely do you see a frightening trap or a capture trap in D&D. Both can remove player agency. A capture trap can be used to drive a plot forward though. An example: The DM needs the characters to negotiate with an orc tribe, and he uses pit traps and net traps to capture the characters in order to facilitate the story.
I suggest adding a couple of more reasons to build traps. The first is alarm. A tripwire attached to a bell isn't made to capture, delay, frighten (although it could double as a deterrent) or kill. It is placed so sentries are warned of intruders before their arrival. Some traps have effects on the trap-maker, not the trap-tripper.
Secondly, a trap may be made to protect something or make it inaccessible. If a diamond on a pillar is protected by a tripwire (or pressure plate, or laser sensor or other trigger) that diamond may drop into a hole that sends it into a vault deeper within the complex. Although similar to a delay trap, this affects the mcguffin instead of the PCs.
Finally, some traps exist only to consume the PCs resources. Tomb of Horrors has 2 (so far!)
As I continue to explore the subject of traps, this list will be expanded. But, as of now, my trap types are:
- Resource denial