Traps: How do they WORK?

Here's something I threw together for the boulder. This is how I see it working in game. This is built with the assumption of a melee heavy party or equally balanced party between range and melee. If you have lots of ranged it probably won't work as well.

The red areas are the path of the boulder (I made it large sized).
The blue areas are the places that the kobolds can trigger the trap.
M = Kobold Minion
S = Kobold Slinger

The PCs arrive from the southwest area.



The kobolds begin by shooting at the PCs (jumping out from cover trying for surprise or whatever). The two closer ones retreat down the corridor to hide behind the trap while the others shoot at the PCs or move to cover if they return fire.

Then one of the minions behind the traps ready actions to trigger the trap when the PCs approach (insert clues for something going on here). The traps roll on the PCs and attempt to knock them down and push them back.

Note that in both boulders, the path is shorter than its movement. It covers some squares multiple times per round.

The kobolds continue shooting at the PCs. The PCs have cover, but so do the kobolds, and the slingers are made for range with the minions using spears, the PCs might have to retreat.

So, what sort of perception check is necessary to notice the trigger for this boulder trap? Or is it 'command detonated' or something? (and why isn't that part of its description?)

Celebrim said:

So, what sort of perception check is necessary to notice the trigger for this boulder trap? Or is it 'command detonated' or something? (and why isn't that part of its description?)

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Well it states:

Perception
No check is necessary to notice the crushing rock.

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So I think you notice it when the trap activates.

Celebrim said:

So, what sort of perception check is necessary to notice the trigger for this boulder trap? Or is it 'command detonated' or something? (and why isn't that part of its description?)

Click to expand...

I assume the trigger will vary based on how the DM wants to set it up. It might use a pressure plate, a lever, a push pin in the wall, or just be hurled by a burly ogre. It doesn't really matter. Keep in mind they're getting rid of the search/disarm type trap in favor of "encounter" traps which challenge the party at the same time. It isn't only a "trap" its a terrain feature.

First thing I thought of when reading this is the trap laden corridor at the beginning of Raiders of the Lost Arc, with the large boulder coming after Indy after he manages to evade all the other traps. So this could be one piece of a series of traps, man, I really like the idea of this...

See Raiders of Oakhurst Reloaded for one possible implementation of this trap ... combined with a wet, winding passage and a couple of archers. Treat the trap as a monster -- it rolls initiative and moves on its count -- that modifies the terrain as it moves.

The thing I don't understand is how the athletics check to avoid it works.

I get the DC 20 check to jump over the rock without running. But if you make the athletics check when the rock comes to hit you, how could you ever make a running (DC 10) jump?

Running is for when you use your move action to move to the boulder and jump over it. Or dive out of the way.

Stalker0 said:

The thing I don't understand is how the athletics check to avoid it works.

I get the DC 20 check to jump over the rock without running. But if you make the athletics check when the rock comes to hit you, how could you ever make a running (DC 10) jump?

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I think the jumping over it is something you'd do on your turn to get past the thing, not something you do reactively to avoid its attack.

Should it worry me that the trap stat block is, so far, more interesting than any monster stat block we've seen?

This looks interesting...