Creates a pit under the target leading straight to the Underworld.

hfspit.lua

	---Creates a pit under the target leading straight to the Underworld.  Type '?' for help.

	args={...}
	
	if args[1] == '?' then
		print("First parameter is target unit id, or 0 to select a location with the cursor.\n  Second parameter is size of the pit in all directions.\n  Third parameter is 1 to wall off the sides of the pit on all layers except the underworld, or anything else to leave them open.  (Leaving them open may allow flying cave-dwellers to path to your fortress if you have normal access to the caverns)\n  Fourth parameter is 1 to add stairs.  Note that stairs are a bit buggy, as they will not reveal the bottom until you dig somewhere, but will still allow underworld creatures to path to your fortress.")
		return
	end
	
	if args[1] ~= nil then
		local unit = df.unit.find(tonumber(args[1]))
	end
	
	if unit then
		pos=unit.pos
	else
		pos=position or copyall(df.global.cursor)
	end
		
	size = tonumber(args[2])
	if size == nil or size < 1 then size = 1 end
	
	wallOff = tonumber(args[3])
	stairs = tonumber(args[4])
	
	--Get the layer of the underworld
	for index,value in ipairs(df.global.world.cur_savegame.map_features) do
		local featureType=value:getType()
		if featureType==9 then --Underworld
			underworldLayer = value.layer
			--print(underworldLayer)
		end
	end
	
    if pos.x==-30000 then
        qerror("Select a location")
    end
	local x = 0
	local y = 0
	for x=pos.x-size,pos.x+size,1 do
		for y=pos.y-size,pos.y+size,1 do
			z=1
			
			local hitAir = false
			local hitCeiling = false
			while z <= pos.z do
				local block = dfhack.maps.ensureTileBlock(x,y,z)
				if block then
					if block.tiletype[x%16][y%16] ~= 335 then
						hitAir = true
					end
					if hitAir == true then
						if not hitCeiling then
							if block.global_feature ~= underworldLayer or z > 10 then hitCeiling = true end
							if stairs == 1 and x == pos.x and y == pos.y then 
								if block.tiletype[x%16][y%16] == 32 then
									if z == pos.z then 
										block.tiletype[x%16][y%16] = 56
									else 
										block.tiletype[x%16][y%16] = 55 
									end
								else 
									block.tiletype[x%16][y%16] = 57 
								end
							end
						end
						if hitCeiling == true then
							if block.designation[x%16][y%16].flow_size > 0 or wallOff == 1 then needsWall = true else needsWall = false end
							if (x == pos.x-size or x == pos.x+size or y == pos.y-size or y == pos.y+size) and z==pos.z then
								--Do nothing, this is the lip of the hole
							elseif x == pos.x-size and y == pos.y-size then if needsWall == true then block.tiletype[x%16][y%16]=320 end
								elseif x == pos.x-size and y == pos.y+size then if needsWall == true then block.tiletype[x%16][y%16]=321 end
								elseif x == pos.x+size and y == pos.y+size then if needsWall == true then block.tiletype[x%16][y%16]=322 end
								elseif x == pos.x+size and y == pos.y-size then if needsWall == true then block.tiletype[x%16][y%16]=323 end
								elseif x == pos.x-size or x == pos.x+size then if needsWall == true then block.tiletype[x%16][y%16]=324 end
								elseif y == pos.y-size or y == pos.y+size then if needsWall == true then block.tiletype[x%16][y%16]=325 end
								elseif stairs == 1 and x == pos.x and y == pos.y then 
									if z == pos.z then block.tiletype[x%16][y%16]=56
									else block.tiletype[x%16][y%16]=55 end
								else block.tiletype[x%16][y%16]=32
							end
							block.designation[x%16][y%16].hidden = false
							--block.designation[x%16][y%16].liquid_type = true -- if true, magma.  if false, water.
							block.designation[x%16][y%16].flow_size = 0
							dfhack.maps.enableBlockUpdates(block)
							block.designation[x%16][y%16].flow_forbid = false
						end
					end
					block.designation[x%16][y%16].hidden = false
				end
				z = z+1
			end
		end
	end

Would merging this into dfhack work as a replacement for needs_porting/hellhole.cpp?