Generate deadly Void below the final bedrock layer

mods/ITEMS/mcl_core/nodes.lua

@@ -21,6 +21,44 @@ minetest.register_node("mcl_core:barrier", {
 	on_blast = function() end,
 })
 
+-- The harmless void directly below the bottom bedrock layer. It doesn't hurt.
+minetest.register_node("mcl_core:void_top", {
+	description = "Void",
+	drawtype = "airlike",
+	paramtype = "light",
+	pointable = false,
+	walkable = false,
+	floodable = false,
+	buildable_to = false,
+	inventory_image = "default_barrier.png",
+	wield_image = "default_barrier.png",
+	stack_max = 64,
+	sunlight_propagates = true,
+	is_ground_content = false,
+	groups = { not_in_creative_inventory = 1 },
+	on_blast = function() end,
+})
+
+-- The deadly void way below bedrock. It hurts very much!
+minetest.register_node("mcl_core:void_deep", {
+	description = "Deep Void",
+	drawtype = "airlike",
+	paramtype = "light",
+	pointable = false,
+	walkable = false,
+	floodable = false,
+	buildable_to = false,
+	inventory_image = "default_barrier.png",
+	wield_image = "default_barrier.png",
+	stack_max = 64,
+	sunlight_propagates = true,
+	is_ground_content = false,
+	groups = { not_in_creative_inventory = 1 },
+	on_blast = function() end,
+	-- Minecraft Wiki: 4 damage each 0.5 seconds
+	damage_per_second = 8,
+})
+
 minetest.register_node("mcl_core:stone", {
 	description = "Stone",
 	tiles = {"default_stone.png"},

mods/MAPGEN/mcl_mapgen_core/init.lua

@@ -479,7 +479,8 @@ minetest.register_on_generated(function(minp, maxp)
 		local data = vm:get_data()
 		local area = VoxelArea:new({MinEdge=emin, MaxEdge=emax})
 		local c_bedrock = minetest.get_content_id("mcl_core:bedrock")
-		--local c_void = minetest.get_content_id("mcl_core:void")
+		local c_void_top = minetest.get_content_id("mcl_core:void_top")
+		local c_void_deep = minetest.get_content_id("mcl_core:void_deep")
 		local c_air = minetest.get_content_id("air")
 
 		for y = minp.y, math.min(maxp.y, BEDROCK_MAX) do
@@ -502,8 +503,10 @@ minetest.register_on_generated(function(minp, maxp)
 					elseif y == BEDROCK_MAX -4 then
 						-- 100%
 						setdata = c_bedrock
-					elseif y < BEDROCK_MIN then
-						setdata = c_air
+					elseif y < BEDROCK_MIN and y > BEDROCK_MIN - 64 then
+						setdata = c_void_top
+					elseif y <= BEDROCK_MIN - 64 then
+						setdata = c_void_deep
 					end
 					if setdata then
 						data[p_pos] = setdata