"That's not a trap, Lidda. That's a pile of Mournland junk."
"You saying I'm wrong, Tordek?"
"I'm saying it's a pile of junk. It's rusted. It's too small to be dangerous."
"Small things can be pretty fierce," said Lidda. "Why don't you walk up to it?"
House Cannith worked on many constructs and mechanical soldier prototypes before its successes with the warforged titan and the warforged themselves. One of the near-misses was a ranged attack call the Camp Guardian -- a design that went terribly wrong and was abandoned by 944 YK. The design papers disappeared at some point after 949 YK.
The original design has been discovered and rebuilt by the Lord of Blades throughout the Mournland. Called the razordisc nightmare by the Lord of Blades, these small devices work off a single powerful spring and are triggered by movement -- but the ones found in the Mournland are able to see even in darkness and sometimes see invisible creatures as well. They never attack warforged or other living constructs.
The razordisc nightmare is a trilaterally symmetrical heap of iron that contains double-jointed throwing arms and a central pillar, all topped by a black set of irises and glass lenses that whir and focus on targets. The internal gearing is simple, but is hidden under a thick layer of camouflage material: scrap iron in the Mournlands battlefields, greenery along more fertile locations, sometimes stony or even brick materials. Spotting a camouflaged razordisc nightmare requires a DC 20 Spot or Search check. Getting close to one requires a successful Hide check (the device has a +20 Spot modifier).
In action, the mithral alloyed arms are powered by three separate mechanisms: one slow but powerful arm throws two discs over distances in trebuchet style, and two faster torsion screw devices hurl one razordisc each but only at close range. The discs that the nightmare throws are round, entirely sharp-edged hunks of steel that spin as they fly to their targets. Some varieties whistle or make a distinct "shirrrrring" noise as they are ejected from the launcher.
Use and Powers
A razordisc nightmare can be set to two modes, either "defensive line" or "ambush mode." When in a defensive line setting, the device fires with its power arm at its maximum range of 180 feet (minimum range 90 feet). The other two arms fire with a range of 60 ft. (2 range increments only, so maximum range is 120 ft. with a -2 attack modifier). The idea of the setting is to protect a battle line with maximum fire against a known foe.
In ambush mode, the razordisc nightmare does not fire until a target is 60 feet or closer, then unleashes the two short-range arms each round. It saves the power arm for targets that are at least 90 feet away.
Unlike triggered single-shot traps, the clockwork nightmare resets itself automatically each round and just keeps firing until it uses up all 40 of its discs.
Original Razordisc Nightmare: CR 4; mechanical; proximity trigger; automatic reset (40 discs total) then manual reset; Atk +10 ranged (1d6+1, disc); multiple targets (fires 2 discs at each target in adjacent 5 ft. squares with range increment 60 ft. (max 120 ft.), plus 2 discs at a single target 90 to 180 ft. away); Search DC 20; Disable Device DC 20. Market Price 10,400 gp.
Lord of Blades Razordisc Nightmare: CR 6; mechanical; proximity trigger; automatic reset (40 discs total) then manual reset; Atk +14 ranged (1d8+1, disc); multiple targets (fires 2 discs at each target in adjacent 5 ft. squares with range increment 60 ft. (max 120 ft.), plus 2 discs at a single target 90 to 180 ft. away); Search DC 21; Disable Device DC 25. Market Price 27,600 gp.
Modifications: If the trap is enchanted with darkvision or see invisibility spells, or both, it has those modes of sight constantly. In this case it becomes a magical item and has the following creation requirements on top of building the device in the first place.
CL 3rd; Craft Construct, darkvision, see invisibility; Price gp base device + 12,000 per spell; Cost 1/2 base device + 6,000 gp per spell + 480 XP per spell.
Razordisc nightmares are used by a group of warforged bandits to ambush House Orien caravans traveling near the Mournlands. The devices are set up along a roadway, camouflaged, and set to tear apart a caravan in a crossfire once it is very close. The party must protect one such caravan from ambush, and destroy the devices and the ambushers. Ideally, the party will pursue the warforged followers of the Lord of Blades to the artificer who is making more of the devices.
As another option, House Cannith might hire the party to recover the plans from the Lord of Blades, ending the manufacture of these things in the Mournlands -- and allowing House Cannith to work on improving the design themselves.
About the Author
Wolfgang Baur is the author of Planes of Chaos, Secrets of the Lamp, Frostburn, Book of Roguish Luck, the Dark*Matter campaign setting, and many other works. He discusses adventure design at the Open Design blog