Thank you for your advice. After reading your tips, I thought some more and I believe that I've really simplified my original design, while still attaining the goal I wish to achieve. I do think that some major improvements could be made though...
A few notes: the pink border isn't anything; I drew it so I could keep my x and y-coordinates on top of each other. It also makes it easier to see where the 0 z-level begins and where the -1 z-level starts. The left picture is the 0 z-level, the right picture is the -1 z-level. Also, "adamantine weapon trap" should read "adamantine menacing spikes set on repeat".
First, I added a staircase to the map, so that when the leader falls down, his fellow goblins will (hopefully) attempt to reach him again by trying to get to the staircase - and to do that, they'll have to step on the spears themselves.
Second, I decided to scrap the whole "lure in water" idea. There is now only one lure, 99% safe from any real danger (unless goblins can shoot arrows through windows)
Third, any aerial creatures can make it through the first two hallways if they're lucky... but then they get mauled by cotton candy spike traps in the main lobby and in the pet area. To save cotton candy, I'll probably only put one or two spikes in each trap. If it's flying, I'm assuming it's not made out of anything tough or absolutely indestructible... right?
Fourth, I switched out A LOT of the walls for windows. There should be no problem with line of sight between the goblins and the bait now.
This new version works a lot like the old one, except after the leader gets beat down the pit, he finds that his only way to the glorious bait is through a gigantic winding maze which I have dubbed "The Intestines of Pain" (ironically, goblins do not feel any pain while they are there). While he walks through the maze, his friends (again, hopefully) stupidly follow him onto the spike traps, and they get tossed off as well. Hopefully, by the time the leader reaches the staircase at the end, his fellow goblins are already at least halfway through the maze. After the goblin goes upstairs to claim the poor animal's life, he finds that he must traverse the cotton candy traps, which are surely more than enough to tear him apart or drop him down to the semi-molten rock. Whichever happens first. After this, his friends will be 100% lost and will simply stand there stupidly, in the maze. It is at this point that I sound the bugle and open the floodgate, drowning all of the goblins in the maze or pushing them back to the deep pit next to the adamantine traps, where they fall to their doom. Instead of connecting the pit to the semi-molten rock layer, I might consider making the pit lead into a cistern over 70 z-levels into the ground instead so that I can gather the goblinite safely after it lands in the pit. In addition, the deep pit will be an automatic evaporating chamber; any excess water will fall down the pit along with the goblins, and eventually all the remaining water in the intestines will evaporate on their own. The only flaws I can see here are:
- goblin safely makes it up the staircase, sees leader die, stands on staircase while the flood rages below, and remains there for all eternity (unless I can somehow get him to move)
- building destroyer comes by the traps, gets knocked down, and proceeds to destroy my floodgate. Since my main base is in a temperate environment, I can simply wait until winter to pick up the pieces and start anew, but this is still an unresolved issue...
If the enemy is trapavoid, it will die when it reaches the adamantine spikes. Nothing really much has changed except for the addition of the stairs on the side; the enemy might dodge onto the stairs, go down, destroy the floodgate, and run back up, but it'll still have to deal with adamantine spikes and giant pits of death.
Again, thank you for your help, it's helped me a lot in my planning