View Full Version : Some ad-hoc traps/obstacles.

2007-03-04, 01:45 PM
This is a question about the use of ad-hoc traps and game mechanics...

For example, if I was to use an immovable rod placed at waist or groin height to block an opponent charging directly at me, or an immovable rod placed in a doorway to make my opponents limbo under it or jump over it, how do you think it should be resolved?

Likewise, if I were to place an immovable rod at about horse-kneecap height in tall grass, or an immovable rod with invisibility cast on it, to break the legs of a horse charging at me, what do you think the game effects would be?

If I cast invisibility on it, would I be able to find it later?

Does anyone else have suggestions for ad-hoc traps or obstacles like this? Take the classic 'piano wire at motorcycle head height' trap used in WWII, or the 'horse-pit' trap (18" deep holes in the ground along an avenue of approach) used in medieval warfare, or the classic fantasy staple of the 'invisible tree knocked down across a road'?

2007-03-04, 03:14 PM
1)Immovable Rod in way of charge - Simple, charging dude need to pass a Tumble check (or needs the Acrobatic Charge class feature)

2)IR in doorway - counts as sqeezing through a space I suppose. count that 5' square as t 5'squares. can't charge.

3)Breaking Horses legs - well, aside from the nastyness of this particuar activity (what did the horse ever do to you?:smalltongue: ), I would rule it as a trap witha reflex save to avoid, maybe. Dunno what damage would be. Possibly 2d6+a trip effect.

4)I I cast invisibilty on it, would I be able to find it later? - only if you remember where you put it. Or wait for the duration to expire. Or search for it.

5)Concealed obstacles to run into all come under the catagory of "Reflex save to avoid being tripped" traps for me. Depending on what it is and how it works, there might be damage involved too (like with the horse one - specifically because the horse is charging and has fairly flimsy legs, I say it causes damage, whereas an invisible tree that you walk into in the road would not, though you might still fall over as a result of walking into it).

2007-03-04, 03:53 PM
The invisible rod at waist height? Unless the first guy had some clue/see invisible he'd always hit it. Damage taken would be based on how fast they were running. If it was at waist height, the first victim would probably end up draped over your invisible bar after. Putting it at head height leaves the problem of guessing the race of your pursuer- halfings just keep going.

Heck, just get a dozen bricks or stones, make them invisible, and scatter them in the middle of a hallway. Invisible caltrops would be exceptionally painful. Old use was to put them in a ford crossing a slow stream- rusty!

The biggest benefit of traps like these is to force your pursuers to slow down and check for the traps. You could always set up another one of these bars on a doorway, and wait at the far end of a hall. When someone gets about halfway to the invisible bar, shoot them with something and slowly walk away. Wait for them to charge at you at full speed... and meet Mr invisible bar.

2007-03-04, 05:27 PM
But what game rules do we apply..?

Seems to me that these are at least CR1 traps - blatantly obvious when you look for them, but when aimed at the unobservant: highly effective. Invisible objects have search DC of ... um... I can't find a reference for that. But if it's 30 or more, our trap CR goes up to 3.

I reckon a person unaware of an immovable object in their path is going to take damage from moving into it if they are running - in this case, they should take 1d6 subdual per 10 feet of base move over 20 feet the character has, Ref save (penalised by losing their DEX bonus - they are running after all) DC 15 for half (this vaguely reflects the falling damage rules, in that acceleration due to gravity [which causes the increase in damage over distance fallen] is near-as-dammit 10 metres per second per second: roughly 30 feet more speed each second - which is also about base human speed).

Movement method (run, walk or hutle) aside, characters who make their REF save against the trap can be considered to have spent double the number of squares thus trapped to avoid the trap. Those who failed their save are considered to have stopped moving at the trap's first square (as well as any effects of the trap: damage, etc), and must begin a new move action next round.

2007-03-04, 05:55 PM
Ummm... if there is _any_ obstacle in the way, you cant charge. If it were invisible, he would hit it, take damage, and end his charge. If it were visible, he couldnt charge. Tumble doesnt play into charge ever, not unless you are homeruling things.

2007-03-04, 08:45 PM
Well, the intent is for field-expedient traps that people drop to screw with the enemy. I don't much care about the CR of the trap, because you'd never use these on their own. As my drill sergeant always told me, and unobserved obstacle ain't an obstacle at all.

How's this for an idea? Spot check to give you a reflex save, DC based on the camouflage of the trap. DC 10 - something like bricks on the ground or an immovable rod in midair. DC 15 - caltrop on the ground, immovable rod in tall grass. DC 20 - deliberately, manually camouflaged objects (caltrops among dirt or gravel; immovable rod in grass with grass laid across it or something). Anything higher could be made by hide skill. Maybe a spot DC 35 for something that could be barely noticed... After, that, reflex save DC something?

Of course, no check for people who wouldn't be looking - someone running away in panic, someone who's never experienced this, a barbarian raging, etc.

Damage for caltrop would be caltrop damage; damage for an immovable rod by altair's post; no reflex check for less damage but reflex check to avoid fallin' on your butt...

OH, and JellyPooga, well, yeah it's mean, but on the other hand it's less mean than the charging individuals intent towards me...

2007-03-05, 11:20 AM
Explosive Runes, lol

i think a flask of alchemists fire placed under a door mat could be interesting, step on it then catch fire.

2007-03-05, 11:44 AM
The DMGII has several booby traps that can be set up from 50gp worth of materials (or scrounged up with a DC20 Survival check in ten minutes) in a minute as a DC20 Craft (trapmaking) check, and rushed to a full-round action for a -10 penalty. They are all CR1/2, but handy enough to use on pursuers or when setting up camp (the nonmagical alarm bells are very handy). Ernest Goes to Camp FTW.

2007-03-05, 01:04 PM
Build a functioning booby trap in 6 seconds?

Good handspeed.

2007-03-05, 06:39 PM
Six seconds? Not difficult for some traps as long as you have the materials handy. Caltrops on the ground, a punji stake or two, a flask of something on a half open door...and those are all without magic. Move Earth, Wood Shape, and Stone Shape will allow you to create other traps in similar time periods.