The fear of "death", its risk each time, is one of the most stimulating parts of the game. It therefore behooves the campaign referee to include as many mystifying and dangerous areas as is consistant [sic] with a reasonable chance for survival (remembering that the monster population already threatens this survival). For example, there is no question that a player's character could easily be killed by falling into a pit thirty feet deep or into a shallow pit filled with poisoned spikes, and this is quite undesirable in most instances.The paragraph above is likely to have been written by the very same author who would later pen S1 Tomb of Horrors; what a difference a few years makes.
- The Underworld & Wilderness Adventure, p. 6.
When you read the list that runs beneath this text, the tricks and traps are definitively different from the list in Appendix G of the Dungeon Masters Guide. It's mostly about confusing mappers and getting PCs lost in the dungeon rather than actually killing them; teleporters, illusions, deceptive corridors, stairs going up or down multiple levels, etc. Whereas by the time Gygax wrote the DMG, it was primarily traps that shoot, stab, burn, drop or poison hapless characters, possibly to their doom. None of this is listed in the OD&D ideas, although there is a pit trap in the sample map. It is not so much an elaboration as a shift in the basic workings of tricks and traps from map hazards to PC killers.
I don't think that it's entirely coincidental that the change occurred after Gygax had started to put out printed dungeons that are very different from his original Greyhawk megadungeon. The difference between Dungeon Geomorphs - which are close to what we've seen of the Greyhawk maps in style - and dungeons like G1, G2 and G3, or B2 and S1, is a shift from dungeons where mapping is a key difficulty to more "logical" (but still nonlinear) dungeons that TSR put out in its heyday. Traps reflected the fact that combat and hazards were more likely to involve PCs getting hurt or killed than lost.
My love for traps stems from the idea that D&D is basically a hidden map game. Both types of trap have the same basic premise: that navigation of the dungeon should be inherently unsafe. A dungeon is an area hostile to intruders; if it weren't, it would already be cleaned out. But the failure state of the "damage" trap is more quickly resolved than that of the "get lost" trap. In the latter case, the referee is opening up the door for a session of players just trying to find a way out. With a damage trap you either get hurt or you don't.
One of the big advantages of damage traps over get-lost traps is that it's easier to create ways to avoid damage traps. If an arrow trap is triggered by a tripwire, then simply not touching the tripwire leaves you safe, trap avoided. You can't really do that with a space distortion corridor (suggested in U&WA) designed to screw up mapping; the referee has just messed with your map but no idea why is given.
None of which is to say that get-lost traps have no place in the game. Dead end corridors, one of the original suggestions, are a great feature - particularly if a wandering encounter begins chasing the PCs at a good clip. One way doors are also interesting, because they force the PCs to find a different way out without getting into the whole, "Hey, you're lost and your existing map is FUBAR." And teleporters are just fun, although I prefer the kind that have to be actively touched - there are several great examples in Stonehell that lead to really interesting scenarios. But on the whole I think that get-lost traps should be used sparingly.
It seems logical to concentrate traps in front of valuable objects or key lairs, but I think this attitude can be mistaken. If traps always come right in front of the treasure, then players will catch on to the pattern. One trick I particularly like is having traps poised before a turn that leads to a dead-end. Intelligent dungeon denizens will only go down such corridors carefully, but they make a great fake-out moment in dungeon design. Logically what these traps are doing is to catch intruders who are unfamiliar with the local architecture.
One thing that OD&D really got right was the rule for triggering traps: "Traps are usually sprung by a roll of 1 or 2 when any character passes over or by them. Pits will open in the same manner." It's a great rule to follow as a referee; you casually roll the die as the PCs are walking; I recommend only rolling once so the flurry of die rolls don't give the game away. Since I casually roll dice frequently in my games it's not noteworthy. And then a session later, the passage that the characters had passed without incident now opens up and someone falls into a pit. It's a great twist, and helps reinforce the idea that the dungeon doesn't become safe with time. Curiously this works much better with the later damage traps than with the get-lost type of traps that OD&D had foregrounded.
I'll finish with this. Traps are a spice in the dungeon, and it's definitely possible to go too far with them. I think putting in a trap in 1/6 rooms (the rate you find in Moldvay's rules for dungeon stocking) is a bit much - also that I don't think many traps should be in rooms proper as opposed to corridors. But a dungeon without them is just bland.
As for tricks, I'll be doing a follow-up focusing on them.