help with traps and CR


Rules Questions


for the most part, I'm pretty ok in both areas, but I ran into 2 things that confuse me at this time....

1. when it comes to determining the CR how would I do that with 3 NPCs , 2 3rd level and 1 7th level, it is possible those levels will change, so id like the exact method known to find that out, its easy with the bestiary due to the xp values being shown, and the short cuts you can use with multiple of the same enemy, but this is the first fight ive planned like this

2. I'm a little lost on how the spiked pit trap works, mostly the 1d4 spikes per target part of when its triggered, I assume the best way for me to understand it, is someone walk me through what I do as a gm when a PC triggers the trap


1) A creature who is a normal race and has class levels has a CR equal to their level -1.

Two 3rd level NPCs are each at CR 2 individually, so their total CR would be 4.

A level 7 NPC is at 6 CR.

So you're going to snowball around a 7-8 CR or so, depending on their exact classes and tactics and if they mesh well together.

Table for CR Equivalencies

The more people you use and the farther they are apart in CR the less accurate the table becomes.

2) This spiked pit trap?

  • Have them make a perception check to notice it. We will assume they all fail their checks.
  • The trap is triggered. Determine who is in the range of the trap (10 by 10 area). Let's assume that the rogue and the fighter were both walking side-by-side so they were both caught by the trap.
  • Have the fighter and rogue roll reflex saves. If a success if rolled, they dodge out of the way and take no damage and do not fall. Let's assume they both fail their reflex saves.
  • You roll 1d4 to determine how many spikes attack each target. Let's say you roll a 1 for the rogue and a 3 for the fighter.
  • Each spike attacks the player's AC (probably flat footed) at their +10 bonus. For each attack that hits (remember one is attacking the rogue and three are attacking the fighter), the victim takes 1d4+2 damage.
  • Each character that falls also takes 1d6 falling damage.

I hope this helps. Any questions?


The best way to find the combined CR of a group is to add up the experience given and find where that falls on exp by CR rewards.

1. For individual NPCs, it's really easy (provided they're a 0 HD race, like human or elf). It's total of class levels. If it's NPC-only classes, CR=level-2. If they have even 1 PC class level, it's level-1. PC wealth by level is +1 CR. Naked is -1 CR. So a level X warrior is CR X-2. Naked is -1, full PC gold is +1. A level X fighter is CR X-1. Same adjustments for naked and with full PC wealth. Solve for X. All from this page, just scroll down.

2. You mean this one?

Everyone in the 10 foot square makes a save (DC 20 Reflex). Everyone who fails falls in and is hit by 1d4 spikes. Roll for each player. Each spike then makes an attack by rolling d20+10 (versus player AC), any that hit do 1d4+2 damage (piercing I guess, though they don't say). That simple.


CampinCarl9127 wrote:

1) A creature who is a normal race and has class levels has a CR equal to their level -1.

Two 3rd level NPCs are each at CR 2 individually, so their total CR would be 4.

A level 7 NPC is at 6 CR.

So you're going to snowball around a 7-8 CR or so, depending on their exact classes and tactics and if they mesh well together.

Table for CR Equivalencies

The more people you use and the farther they are apart in CR the less accurate the table becomes.

2) This spiked pit trap?

  • Have them make a perception check to notice it. We will assume they all fail their checks.
  • The trap is triggered. Determine who is in the range of the trap (10 by 10 area). Let's assume that the rogue and the fighter were both walking side-by-side so they were both caught by the trap.
  • Have the fighter and rogue roll reflex saves. If a success if rolled, they dodge out of the way and take no damage and do not fall. Let's assume they both fail their reflex saves.
  • You roll 1d4 to determine how many spikes attack each target. Let's say you roll a 1 for the rogue and a 3 for the fighter.
  • Each spike attacks the player's AC (probably flat footed) at their +10 bonus. For each attack that hits (remember one is attacking the rogue and three are attacking the fighter), the victim takes 1d4+2 damage.
  • Each character that falls also takes 1d6 falling damage.

I hope this helps. Any questions?

yeah that mostly clears it up, for whatever reason the fact that you were essentially rolling the d4 to see how many attacks were made was what went over my head, reading this though, a new question has arose, 10 by 10 area, was that a miswording or is it legit 10 by 10, cause how I read it, I assumed it was 2 5 foot squares beside eachother, but hen I hear 10 by 10, it makes me think its 4 squares in total, in a square of 4 5 foot squares, which I could just be analyzing that completely wrong, just wanted to clarify what the actual area of effect was


It's meant to be a 10ft square, so 4x5ft squares is correct; as GM you might adjust that to better fit your encounter, depending on the layout and other items and creatures in the room.


Yes, it is four squares in total. Pathfinder will make engineers cry sometimes with how they explain dimensions.


CampinCarl9127 wrote:
Yes, it is four squares in total. Pathfinder will make engineers cry sometimes with how they explain dimensions.

pathfinder is awesome, but agreed on the fact that navigating and understanding these books at times is awful, like I feel normally its perfectly explained, except for the fact there would be something else mentioned earlier only in one sentence, that if you didn't memorize it fully, then you fail to understand lots of other things, like how the only thing that really makes mention of adding the CON modifier with hit dice when you level and stuff, is only in that constitution section at the beginning, when a reminder in the leveling up section, wouldn't have killed anyone, also why I bring any questions I have to here, I'm sure I could figure it out, if I fumbled the book for an hour or more, but id rather just get an instant understandable answer, perhaps that's lazy though >.>


Pathfinder is definitely a very complex game that takes a lot of reading and cross-referencing to fully understand. You shouldn't feel bad at all about asking questions here, we are happy to help!

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