Traps should be interactive for the players, and there should be the possibility of a reward if a player finds a clever way to bypass the trap, and or repurpose it to use it against enemies. A trap which merely decreases some of the PC's hit points can be a useful mood-setting device, but without interaction it leaves players feeling like it was just that -- a hindrance thrown together by their DM to keep them on their toes. However, even the most mundane and simple trap can instantly become interesting if you add meaningful interaction with the trap and its effects.
I totally disagree. Traps are not placed to provide something interesting for the players to do, and lack of interaction should never feel like a hindrance thrown together by the DM. If it does then the trap placement is either illogical, or it's overpowered or otherwise doesn't make sense. Traps are placed by somebody who wants to prevent somebody else (the characters) from doing something, whether that's entering an area, taking something, sneaking up on them while sleeping, etc.
The reward is not getting caught by the trap, and finding a clever way to bypass it is a bonus. It's not something that needs an additional reward.
Interaction with the world, including traps, is just part of good DMing. Be creative. If the characters are moving at a normal pace, detection by passive perception could be noticing that one of the floor stones moved ever so slightly and you hear a 'click.' Instantly stops them in their tracks and now they have to figure out how to handle it. The trap is a boring old pressure plate trigger with some payload. But suddenly the tension has risen measurably, and one character is potentially taken out of the process of disarming it (even more interesting if the lead character was the rogue...).
Even if they fail their perception, 'you feel the tug of a tripwire and there's a quick swishing sound like a rope that was suddenly released. What do you do?' Make them give you an answer quickly, or they lose their opportunity. Otherwise go with their description and it probably involves a Dexterity save to avoid.
If they are moving at a slower pace and keeping their eyes open, and tapping the stones ahead of them, then they might notice something isn't right. I often tell them just that, 'something about the hall just feels wrong, you can't put your finger on it.' Let them describe what they do and then go from there. You don't have to tell them 'you find a trap' just because passive perception said they noticed something. They just know something isn't right, and they'll need to investigate further to find out what.
I recently used the classic greased sloping hallway. They noticed the small holes at the floor, and the druid turned to a centipede to investigate them, and found they were short and ended in a wall, or possibly little door, but the hole was slippery. They would have probably noticed earlier if there was a dwarf in the party, but they felt the floor shift as enough of them passed over the fulcrum. Some of them tried to run back, some forward - enough to cause it to start to dump them to the next level. The funniest part was the rogue, who has boots of climbing and springing jumped onto the wall. The other rogue grabbed his whip to try to grab whatever. The only thing to grab was somebody, and with a random die roll, grabbed the rogue on the wall...who rolled a 1 on his Strength save to avoid being pulled off his feet, and they both went down, and the party was split between two levels.
1) Made by primitive creatures, and < deadly is all they can manage
2) Meant to scare and not kill
3) Was deadly, but lost potency over time
4) It is deadly by the character's skill reduces the lethality
I've used all of these, and they are great answers.
Some traps or particularly alarms may even be visible. They are simply deterrents, and are meant to slow you and potentially alert somebody else. They might cause some damage, but the intent isn't to kill.
In fact, a lot of traps may be less than deadly because most people would not feel comfortable setting a trap that will automatically kill. Incapacitate, yes.
For a deadly trap, the vast majority of people could be killed with a couple of crossbow bolts or poison. There is little reason to design or build one that will do 50+ hit points of damage because it's unnecessary.
I've also hinted that traps may be present by having a trap or two that has already been triggered. Somebody else already tried to plunder the crypt and they didn't survive.
Traps can also misfire. Unless it's a trap that can be reset, or automatically resets, it may not have ever been tested.
Think of what the trap setter is trying to protect, or prevent somebody from doing. Then think about who they think will be trying to bypass the trap. For example, traps in Thay would most likely need to be able to incapacitate, slow, or kill a wizard, since there's a good chance that the unwanted individual may be one.
Think about it from the trapbuilder's point of view. Acerak and Halaster notwithstanding, the typical trapbuilder is not just trying to kill people for the lulz. The trap is a means to an end; protecting something or someone.
- If the trap is blocking access to something valuable, there must be a way to disable or bypass it. Otherwise, how can you get to the valuable thing to use it? And what looks to the trapbuilder like a necessary off switch looks to the PCs like a puzzle.
- Traps are not cheap or easy to build. Most thieves will die to a single glyph; are you really going to spend thousands of gold to pile on half a dozen, on the off chance that someone comes along who's able to survive one glyph, yet unable to detect and disable them?
- You, the trapbuilder, might trigger the trap by accident. If that happens, it's nice if the trap is not instantly fatal--the ideal trap would include some provision for disabling it after it's been triggered and before it delivers the killing blow. Again, what looks to the trapbuilder like an emergency safety protocol looks to the PCs like a puzzle to solve.
I agree with all of these, with the possible exception of the last option. However, if the trap builder is for hire, they very well may place a hidden bypass for themselves.
Ilbranteloth
