Page 123 - DnD 5e - Xanathar's Guide to Everything

TRIGGERS
The advice on triggers given for simple traps also ap-
plies to complex traps, with one exception. Complex
traps have multiple triggers, or are designed such that
avoiding a trigger prevents intruders from reaching the
area the trap guards. Other complex traps use magical
triggers that activate on specific cues, such as when a
door opens or someone enters an area without wearing
the correct badge, amulet, or robe.
Look at your map and consider when you want the
trap to spring into action. It's best to have a complex trap
trigger after the characters have committed to exploring
a n area. A simple trap might activate when the charac-
ters open a door. A complex trap that triggers so early
leaves the characters still outside the trapped room, in
a place where they could decide to close the door and
move on. A simple trap aims to keep intruders out. A
complex trap wants to lure them in, so that when it acti-
vates, the intruders must deal with the trap before they
can escape.
The trigger for a complex trap should be as foolproof
as you can make it. A complex trap represents a serious
expenditure of effort and magical power. No one builds
such a trap and makes it easy to avoid. Wisdom (Per-
ception) and Intelligence (Investigation) checks might
be unable to spot a trigger, especially a magical one, but
they can still give hints about the trap before it triggers.
Bloodstains, ashes, gouges in the floor, and other clues
of that sort can serve as evidence of the trap's presence.
INITIATIVE
A complex trap acts repeatedly, but unlike characters
and monsters, traps don't roll for initiative. As mechan-
ical or magical devices, their active elements operate in
time its active element is triggered. As water floods a a periodic manner. When designing a complex trap, you
chamber, the characters must swim across areas they need to decide when and how often its active elements
could walk through just a round or two earlier. produce their effects.
Since a complex trap remains active over the course In a trap with multiple active elements that work in
of several rounds, it might be possible to predict its concert, those different elements would act on different
future behavior by examining how it functions. This initiative counts. For instance, on initiative count 20,
information can give its targets a much better chance of blades sweep across a treasure vault, driving the charac-
thwarting it. To minimize this possibility, design your ters back into the hallway. On initiative count 10, magic
trap so that it presents multiple threats that can change darts fire from statues in the hallway while a portcullis
each round. The changes can include how a trap targets falls to confine the characters.
creatures (different attacks or saving throws), the dam- Initiative 10. If a trap's active element takes time to
age or effects it produces, the areas it covers, and so build up its effects, then it acts on initiative count 10.
on. Some traps might have a random effect each round, This option is good for a trap that functions alongside
while others follow a carefully programmed sequence allied monsters or other guardians; the delay before it
of attacks. acts can give guards the chance to move out of its area
Dynamic elements usually occur according to a sched- or force characters into the area before the trap triggers.
ule. For a room that floods, you can plan out how the Initiative 20. If an element is designed to surprise
rising water level affects the area each round. The water intruders and hit them before they can react, then it acts
might be ankle deep at the end of the first round, knee on initiative count 20. This option is generally best for a
deep the next, and so on. Not only does the water bring a complex trap. Think of it as the default. Such a trap acts
risk of drowning, it also makes it harder to move across quickly enough to take advantage of most characters,
the area. On the other hand, the rising water level might with nimble characters like rogues, rangers, and monks
allow characters to swim to the upper reaches of the having the best chance to move out of the area before
chamber that they couldn't get to from the floor. the element activates.
Dynamic elements can a lso come into play in reaction Initiative 20 and 10. Some active elements are in-
to the characters' actions. Disarming one element of the credibly fast acting, laying waste to intruders in a few
trap might make the others deadlier. Disabling a rune moments unless countered. They act on initiative count
that triggers a fire-breathing statue might cause the
20 and 10.
statue to explode.

CHAPTER 2 ( DUNGEON MASTER'S TOOLS