Fear.

Fear is a trapsmith’s ally, as nothing deters tomb robbers better than seeing a valued comrade perish in the most gruesome way possible. A trapsmith asks intruders a simple question: “Is this carnage a price you are willing to pay, to progress further?” If the trapsmith is good at his job, he will only need to ask the question once.

For example, consider the basic arrow trap. Can it be made deadlier, while retaining the same CR? Of course! Here’s how to set it up.[More…]

Basic Arrow Trap: CR 1; mechanical; proximity trigger; manual reset; Atk +10 ranged (1d6/×3, arrow); Search DC 20; Disable Device DC 20. Market Price: 2,000 gp.

Is this a trap that will get a resounding “no” on the trapsmith’s question? No. The basic arrow trap is a venerable design, but it lacks the brutality to achieve the desired answer, frightening intruders away. For 2,000 gold pieces, you get one arrow. Sure, the trap can target flyers, but if something can fly, one arrow will not be enough to stop it dead in its tracks. The trap has a manual reset, but who will perform that reset?

Let’s improve on the basic arrow trap, without overcharging the customer. The first thing to go is the proximity trigger; other traps can deal with flyers. The manual reset can be cut as well, you only have one arrow, one shot, in the end, it is cheaper to buy and install a new trap. As a consequence, if a trespasser finds the trap, it just isn’t worth it to make it hard for him to disable it. He can have his little victory, because trap number two is waiting around the corner.

Gargantuan Arrow Trap: CR 1; mechanical; location trigger; no reset; Atk +14 ranged (4d6/×3, arrow); Search DC 20; Disable Device DC 8. Market Price: 100 gp.

Increasing the size of the weapon that targets the intruder is usually the most efficient method to get a “no” on the trapsmith’s question. Nothing says “Get out” better than hurling a small, pointy tree at unwanted guests.

DM tip
Hurling a gargantuan arrow at a 1st level character is quite dangerous. Consider hurling it at PCs of at least 3rd level — without granting too many XP. The gargantuan arrow trap is a cheap way, in terms of XP, to set the scene for a particular environment and create a sense of danger. Whether you hit or miss, the PCs will know to be careful.

If you want to add an extra twist, have the firing mechanism set off a bell or alarm, bringing monster to the scene just when the party is trying to heal a grievously wounded comrade.

Design notes
Location trigger: Costs us nothing and is a better choice than the proximity trigger.

No reset: This is a one shot trap of terror, plus the lack of reset pays for some of the upgrades later.

Attack +14 ranged (4d6/x3): we spend the money we saved on the reset on the attack roll instead to make sure that the arrow hits. The arrow is for a gargantuan longbow, or really any tree with a sharp point on it. Note that we keep the attack bonus under the CR increasing level of 15. The arrow’s average damage is 14, giving it a CR 2 rating.

Search DC 20: we have only one shot, so we have to make sure that finding the trap is hard.

Disable Device DC 8: if the trap is found, all is lost, so by decreasing the DC we save hundreds of gold pieces in cost and we gain a -1 CR modifier.

Overall, this CR 1 (base 2 and -1 for the low Disable score). The trapsmith strikes again!

Like to see more traps? Let us know in comments!