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[Elvang]

The Practicalities of Fire Imp Defense
An Empirical !!Treatise!!
By Obok Mengthulokil, Clerk

The Goal
Reusable fire imp based defense regardless of grass presence with little to no player interaction needed.
The Creature and Acquisition
Fire imps are small humanoid creatures found in medium to large sources of magma everywhere. These aggressive magma-dwellers are often a source of vexation for any dwarf who wishes to make full use of their magma supply, as fire imps possess the unique ability ziril gasol, or fire breath. While their bones are valuable, the meat remains warm to the touch and more than one dwarven kitchen has been lost to spontaneously combusting fire imp fat.
The main course for capture is the placement of one or more cage traps around the magma source. The cage need not be made out of any special material, a Feather Tree Cage is as capable of holding one or twenty fire imps just as well as a ¤Steel Cage¤. Narrowing the possible exits available to a fire imp in your magma as well as providing bait, noble or chained creature, will increase the likelihood of capturing the imp. Be aware that fire imps do not breed at all, nor do more migrate to your area.
Notes

• Size = 3
• Speed = 900
• Crossbow range = 20 tiles
• Blood Type = Goo
• Will not fire while chained
• Will not fire through fortifications/grates/bars
• Will not fire across Z-Levels
• Will not fire across channels
  
• Must be able to path to target
• Fireball range is same as crossbow range
• Opens pet-impassable doors
• Further Reading
  

The Defenses^{+Practicality}

Spoiler: Chained Imp (click to show/hide)

Fire imp is chained out in the open.

Caged	Uncaged

Fire imp refuses to engage the test subject at all. High chance of escape during transfer.
Result: Impractical, One Escape

Spoiler: Same Z-Level Pillbox (click to show/hide)

Fire imp is placed in a walled off section with one or more fortifications.

Caged	Uncaged

Fire imp refuses to engage the test subject at any range.
Result: Impractical

Spoiler: Difference of Z-Level Pillbox (click to show/hide)

Fire imp is placed on a balcony with no exit overlooking the target. Both fortifications and channels were tested.
[

Caged	Uncaged

Fire imp refuses to engage the test subject at any range.
Result: Impractical

Spoiler: Bridge Gap (click to show/hide)

Fire imp is placed on a balcony with a retracted bridge, test subject is on the same z-level.

Caged	Uncaged

Fire imp refuses to engage the test subject at any range.
Result: Impractical

Spoiler: Resetting Corridor 1.1 (click to show/hide)

Fire imp is placed in a corridor with two drawbridges, and one side with fortifications/channel. Additionally, there are two pressure plates that are linked to the bridge they are placed near.

Caged	Uncaged

Fire imp only occasionally moves, will not fire through fortifications. If it does launch a fireball, it is usually at something it saw past the bridges, thus allowing it enough time for the bridge to reset and escape.
Result: Impractical

Spoiler: Resetting Corridor 2 (click to show/hide)

Similar setup as Resetting Corridor 1.1, except there are now grates above a portion of the corridor.

Floor 1	Floor 2

Fire imp will not fire through grates at test subject.
Result: Impractical

Spoiler: Resetting Corridor 3.1 (click to show/hide)

Similar setup as Resetting Corridor 1.1, except there are now fortifications on the side with the bridges.

Caged	Uncaged

Fire imp continually moves from bridge to bridge if test subject is visible from fortifications but not bridge. Fire imp would not fire through fortifications. During testing, test subject was crushed by bridge.
Result: Impractical, Test Subject Died

Spoiler: Resetting Corridor 1.2 (click to show/hide)

Similar setup as Resetting Corridor 1.1, except channels have replaced the fortifications.

Caged	Uncaged

Fire imp does not move, nor will it fire across the channel at any range.
Result: Impractical

Spoiler: Resetting Corridor 3.2 (click to show/hide)

Similar setup as Resetting Corridor 3.1, except channels have replaced the fortifications closest to the bridges.

Caged	Uncaged

Fire imp doesn't reliably move as in Resetting Corridor 3.1, nor will it fire across the channel at any range. Additionally, Microcline was struck while channeling.
Result: Impractical, Struck Microcline

Spoiler: Pet Corridor 1.1 (click to show/hide)

Similar setup as Resetting Corridor 1.1. Space has been minimized, and there are now chained pets as bait just behind the bridges.

Caged	Uncaged

Video
Fire imp immediately moves towards one of the chained pets and opens fire ~5 tiles away. Hits locked bridge and begins moving towards other pet. Unfortunately the imp turns around once the bridge is down and immediately fires again upon the same pet, before killing it and escaping. Good for 2, maybe 3 shots. Version 2 of this design is planned.
Result: Slightly Impractical, Single Use Fire Starter Trap

Spoiler: Pet Corridor 2.1 (click to show/hide)

Similar setup as Pet Corridor 1.1. Additional pressure plates toggle gears, which in turn move water on/off a pressure plate that activates a second bridge. Result is a longer lasting line of sight obstacle.

Caged/Links Z-0	Caged/Links Z+1

Video
Fire imp immediately moves towards one of the chained pets and opens fire. Steps on second pressure plate toggling gears. Water is moved onto pressure plate, activating second layer bridge. Fire imp hits bridge, begins moving towards other target. Bridge opens, fire imp hits pressure plate toggling gears again. Fire imp hits pressure plate for the opposite side bridge as the second layer bridge now opens. Repeats until fire imp got out of sync with bridges, perhaps moving the second set of pressure plates further apart might fix this. Additionally, fireball does not travel further than the target. Version 3 will attempt to remedy these problems, plus Alcohol.
Result: Dwarvenly Impractical, Complicated

Spoiler: Silk Farm Setup (click to show/hide)

Setup similar to a silk farm where the door is pet-impassable.

Caged	Uncaged

Fire imp opened door regardless, refused to fire through fortifications and channel.
Result: Impractical, Escaped Imp

Spoiler: Hatch Corridor 1.1 (click to show/hide)

Setup where imp has several possible paths to target, but each path is only possible because of a hatch. Link said hatch to a pressure plate placed right before it.

Caged	Uncaged

Video 1, 2
Fire imp immediately begins firing on target, and continues to do so with no problem. Never escapes. Small setup, Video 2 details a version where you don't have to worry about melee. Only problem is ranged attackers as the Imp still refuses to fire through fortifications.
Result: !!Practical!!

[Diamond]

Nice work there.
As far as I see any defenses involving fire imps are impractical. Dragons are really better at this, I use them often. Try comparing those creatures to find out the difference, other then flying and fire breathe range. Maybe that will help some way.

[Innominate]

It is my suspicion that fire imps will only engage if they can path to the target. If this is the case, you would probably need a container that opens and closes rapidly. The timing of this I suspect would be extremely difficult.

[dogstile]

It is my suspicion that fire imps will only engage if they can path to the target. If this is the case, you would probably need a container that opens and closes rapidly. The timing of this I suspect would be extremely difficult.

Unless it was a rather long corridor, say... 300 tiles long?

[wagawaga]

I guess you can use the GCS silk farm approach, putting a pet-impassable but not forbidden door, so that the imp can path to the enemy but cannot reach him.

[bmaczero]

Or possibly the reverse, just stick a room in front of your entrance locked up by pet-impassable, not-forbidden doors and wait for the enemy to walk into it.

[Elvang]

Nice work there.
As far as I see any defenses involving fire imps are impractical. Dragons are really better at this, I use them often. Try comparing those creatures to find out the difference, other then flying and fire breathe range. Maybe that will help some way.

Yea, I've captured all the fire imps on my map as I'm about to magmatize my fortress (dwarfmade volcano fortress). Wanted to do a fire imp defense but all the info on that was theoritical designs or stuff that just wouldn't work. Since it comes up fairly often I figured I'd clear any of the misconceptions about it.

I'll have to see if there are any dragons left in my world so I can test it or if I need to gen a new one, I can run them through all the same tests for effectiveness.

It is my suspicion that fire imps will only engage if they can path to the target. If this is the case, you would probably need a container that opens and closes rapidly. The timing of this I suspect would be extremely difficult.

The resetting corridors allow the imp to path to freedom, they are timed so the bridge 9 times out of 10 closes the second the imp is on the tile before it (otherwise a little earlier). That's why the imp's movement speed is listed in the notes. Raw speed/100 = how often the creature can move. The corridor is based on a trap that was posted here a while back, that prevented a goblin from ever reaching freedom as it pathed endlessly, couldn't find the thread unfortunately as it had a nice video of it in action.

Unless it was a rather long corridor, say... 300 tiles long?

I minimized the distance between the trigger and the blocking object, I could probably make it even smaller to allow for more imps in a smaller entrance, but I moved on after it became an Impractical defense.

I guess you can use the GCS silk farm approach, putting a pet-impassable but not forbidden door, so that the imp can path to the enemy but cannot reach him.

Or possibly the reverse, just stick a room in front of your entrance locked up by pet-impassable, not-forbidden doors and wait for the enemy to walk into it.

Fire imps can open doors, so I'd assumed that was the same behavior as invaders (opening forbidden doors, no idea about only pet-impassable). I'll add it as one of the test just to be sure though.

[Retro]

This is a great study! I've been trying to capture the last reluctant imp on my current fort rather than kill it exactly for the purposes of pillboxing it, but it seems it's rather worthless.

[smjjames]

Speaking of fire imps, I haven't seen any in a very long time, they never seem to appear in the magma pipes or pools that I've embarked on. No idea why.

[Elvang]

Updated with 2 new designs. I have a good feeling about Pet Corridor 3.1, after looking at it a bit I know how to simplify it somewhat while increasing the length of time the bridge stays closed. Soon I'll be at the booze tests, been brewing sunshine just for this .

EDIT: Forgot to try the silk farm setup, that's now up there too.
Definitive conclusions so far:

• Will not fire while chained
• Will not fire through fortifications/grates/bars
• Will not fire across Z-Levels
• Will not fire across channels
• Must be able to path to target
• Fireball range is same as crossbow range
• Opens pet-impassable doors

[expwnent]

Will imps open pet-impassible doors if they are pets?

[Grendus]

Hmm.

It seems to me that the most dangerous thing about fire imps isn't their fireball, it's their ability to light the map on fire. It might be possible to make use of that even with the trap's current... limitations.

We need a way to get fire across or out of an area that can't be normally pathed out of. I can think of a few ways, although none are pretty. You could drop a kitten onto a chunk of coal, then drop the coal down a z-level onto the ground. You could try this:

WWWWWWWWWWW
.....k......c...........IW
WWWWWWWWWWW

Where k is a kitten, c is a cage trap, and I is a fire imp cage linked to a lever. Fire imps always start by throwing fire, so he'd ignite the kitten then get caged. Use a fireproof cage (since that fire he ignites will likely spread back to the cage trap, I've lost wooden cages that way) and watch the fire go bake invaders. The only danger is if the invaders get to the kitten first or fall into the cage trap after you pull the lever.

[Elvang]

Can't work on it more today, but this is how far I got with version 3, Video. The booze wouldn't ignite in either the iron or wood barrels. The fireball even stops on the wooden barrels.

[jryan]

Here is how I would do the Imp Pillbox:

Code: [Select]

#######
#######
##+++##
##+i+##
##+++##
#######
#######
i = Imp
+ = Fortification
# = Channel

This provides the imp full protection from meleers while giving him a slight advantage against ranged attackers as well.

Now you just need a setup that will funnel the enemy around the imps like...

Code: [Select]

===#######   #######===
   #######   #######
   ##+++##   ##+++##
   ##+i+##   ##+i+##
   ##+++##   ##+++##
   #######   #######
   #######   #######

In this case the invaders will have to pass between the two imps... this setup also works for marksdwarves.  Though in their case you should make a slightly larger pill box to accommodate a barrel of ammo.

[gtmattz]

^^^ You should have read the original post, imps apparently do not fire through fortifications or over channels, thus rendering the pillbox concept unworkable.