Have you ever wondered how to make a new trap. There are a bunch of traps out there and different tables. But how do you make your own? How about I walk you through making a trap for The Pathfinder Roleplaying Game (but you can use for other RPGs).
Iron Pellet Grenade Trap CR 5
Type mechanical; Perception DC 26; Disable Device DC 26
Trigger touch; Reset none
Effect mechanism lights and drops an iron pellet grenade onto the floor (Iron Pellet Grenade, 1d6 bludgeoning damage, 1d6 piercing damage, and 1d6 fire damage, DC 15 Reflex save for half damage); onset delay (1d3 rounds); multiple targets (all targets in a 10-ft.-radius burst)
Cost 2500 gp
Craft (Traps) DC 20
So, how did I build this? Well, using the rules from our handy rule books (You will find this information in ‘The Core Rulebook’ under the ‘Environment’ section), we just look up a few simple variables. Let me break it down for you.
Damage: Because the Iron Pellet Grenade deals 3d6 damage (1d6 each bludgeoning, piercing, and fire), we get an average of 10.5 damage. There is a +1 CR to a trap for every 10 points of average damage. If the trap can hit multiple targets, you double the CR bonus. In our case: +2 CR
Perception: A fairly equivalent DC for perceptions on trap spotters is going to be between 24 and 27 for our CR. At 26 for perception, we are given a CR +2.
Disable Device: Many traps have similar perceptions and disable devices (because both skills will tend to be similar on characters from a ‘skill ranks’ stand point). Because of this, we are keeping a DC 26 on the disable device check. At 26 disable device, we get another CR +2.
I know, I know, That equals CR 6. What did I forget?
Well, we go back to our grenade. The grenade itself has no attack roll (not CR change), but it does have a built in Reflex save (DC 15).
And? Well, we go back to our trap tables and find that a Reflex DC 15 is a CR -1 modifier. Take that away from our CR 6, and we are now at a CR 5 trap. Other factors that do not change our trap CR are: onset delay (again, from the grenade), trigger (we have touch), reset (none), and the type being mechanical.
XP, cost, and craft DCs are much easier. Every CR 5 challenge rating is worth 1,600 experience points. Check! The cost of a mechanical trap is equal to CR x (either 250 gp for easy/somewhat primitive or 1,000 gp). In our case, it is the latter which would be 5,000 gp; however, our trap cannot be reset which cuts the cost in half to 2,500 gp. We also see in our trap building tables that the base craft DC on Traps with a CR 1-5 is 20 (and we have no additional elements to increase that).
Now, that wasn’t so hard, was it? Hope you can use it in your next adventure!