Level and Threat. A trap’s level is actually a range of levels, equivalent to one of the tiers of play
(levels 1–4, 5–10, 11–16, and 17–20), indicating the appropriate time to use the trap in your
campaign. Additionally, each trap poses either a moderate, dangerous, or deadly threat, based on
its particular details.
Trigger. A simple trap activates when an event occurs that triggers it. This entry in a trap’s
description gives the location of the trigger and the activity that causes the trap to activate.
Effect. A trap’s effect occurs after it activates. The trap might fire a dart, unleash a cloud of
poison gas, cause a hidden enclosure to open, and so on. This entry specifies what the trap
targets, its attack bonus or saving throw DC, and what happens on a hit or a failed saving throw.
Countermeasures. Traps can be detected or defeated in a variety of ways by using ability checks
or magic. This entry in a trap’s description gives the means for counteracting the trap. It also
specifies what happens, if anything, on a failed attempt to disable it.
MAKING TRAPS MEANINGFUL
If you want to improve the chance that the characters will come up against the traps you’ve set
for them in an encounter or an adventure, it can be tempting to use a large number of traps.
Doing so ensures that the characters will have to deal with at least one or two of them, but it’s
better to fight that urge.