This walkthrough is for Overlord; the ninth and final level in Lunar Apocalypse
Overlord starts underwater and continues on from where Dark Side left off. If you don't have scuba gear, you'd be best to get out of the water quick; swim forward and surface when you reach the centre. If you want the atomic health stay underwater ;you will need to go to the other side of the room where you will see a hand imprint on the wall. Push it. Once you push it, you will hear a rather loud noise coming from behind you. Turn around, and you will see the column in the middle of the room will have opened up, revealing an Atomic health. This step isn't necessary but you might need it. Anyway once you're done underwater surface.
You'll now be in a circular room with several enemies. Once you take them out look around the room for a door with an alien switch on it. When you push the switch it will open the door.
Going through the door reveals a small hallway with a door, but you won't get to see the door much at first, because it's being guarded by a Mini Battlelord. You'll have to take him out to get by. There is also exploding canisters here which will take out a large section of wall, so be careful you don't get caught up in that explosion trying to take out the Battlelord; a good option to neutralize the threat of being blown up by the canisters is to throw a pipebomb round the corner without being seen by the Mini Battlelord leave the hallway and then detonate the pipebomb; the resulting explosion will damage the mini battlelord but be careful as the Mini Battlelord might be in the hole in the wall trying to find you. You can also lure the Mini Battlelord to the circular room you were just in as it might be easier for you to avoid his attacks.
Anyway after taking out the Mini Battlelord, you will go through the door he was guarding and find yourself in a room near a waterfall. Don't follow the water, you need to go up the ramp you see in the far side of the room. However you can go underwater if you wish to explore it before proceeding further in the level.
After you make it up the ramp, you will come to the second level of this room. Things will attack you from all sides, so be prepared for a lot of combat. Once things have settled down, make your way past the babe and the slimer eggs.
This will lead you to another ramp, and the way up to the top most level of the room. When you get up there you will see some aliens guarding several captured babes and slimer eggs.
Behind the hanging babes is a switch you need to flip. This switch deactivates a forcefield preventing you from getting to the final area of the level. Once you have flipped the switch, you will need to make your way back down the ramp you just used to come up to this part of the room. When you come down the second half of this ramp, you will see a vent cover on the wall that you've most likely seen on the way up.
Take out the vent cover, as well as the trooper that is hanging out around in there. This will reveal a passageway which had previously been blocked by a forcefield. Go in there, and you will be looking out over what appears to be a slow spinning fan; some Octabrains will also try to kill you. You'll also notice a couple of different passage ways near the fan; you can follow them if you want to explore the level a bit more before jumping down.
The Overlord is in the chamber below. So when you're ready jump down; the spinning fan is unlikely to kill you but sometimes it can if you don't time things properly. Of note there's also atomic health on top of the spinning fan which you might find useful
Once you are in the Overlord chamber, you will be surrounded by exploding canisters and slimer eggs. Many if not all of the eggs will immediately hatch, and slimers will come towards you. You'll also see a large door; this is where the Overlord is. It's advisable that you shoot a canister which will cause a chain reaction that will take out most of the slimers and eggs as you wouldn't want those things trying to latch on your face while fighting the Overlord; if you do this quick enough; there's a good chance you'll kill them all; a pistol is the best choice as a pipebomb will not cause all the canisters to explode.
Before going up to the door where the Overlord is there's something that can really help you in your battle with the Overlord if you do it before you release him. Over to the left of the chamber room is a crack in the wall. Jump in there:When you jump in there, you will end up in some water. Go all the way to the bottom of the water, and you will find several items here that will be of use. There is a jetpack which can be used to go back up the fan drop if you run out of weapons and health , a medkit, and a Devastator weapon. All of which will be useful against him.
Now whenever you're ready walk up to the door which will automatically open and the Overlord will be released into the room. Whenever you do start fighting the Overlord Circle Strafing and shooting are the best way to take him down as you certainly can't stay still as he's quite accurate with his twin rocket launcher. There's also some items in the room he was in but be quick as a barrage of rockets is sure to follow you when you go in.
When you beat him you'll be rewarded with a cutscene and a message from the Cycloid Emperor revealing that the aliens operations in space was a diversion to keep Duke Nukem busy while they rallied their forces on earth. It's now time for Duke to return to earth and kick more alien ass in Shrapnel City.