Eradicator/The Core

At last it's time for the final showdown. You enter in a short corridor that goes off to the left. Just before the corner, look for a misaligned texture on the left wall: there's a secret area here. Once you enter the big chamber that's just ahead, this area will be closed off but will reopen when G'or is defeated. The main chamber is a tall area whose floor is flooded with sludge, and an upper level with a wide ledge and bridge and many platforms floating in the air you can jump to. There's ammo scattered everywhere, but not a lot of health (no full ones).

"It ends now!"
It turns out G'or is a big ugly flying something, and shoots these nasty smoking cinder projectiles. They do a lot of damage but are easy enough to dodge, however you absolutely MUST use strafing if you're a player who normally doesn't. The architecture in here is a pain in the butt and you'll probably end up having to fight it at least some, but fortunately G'or himself isn't very hard to kill although he can dodge pretty quickly. (Maybe the annoying architecture is supposed to be compensating for this.)

When you first see G'or, use your Death Sphere on him right away if you saved that last one from the previous level, and maybe set off a Missile Hunter-Killer or two. Then cross over the sludge on either side to the big lift in the far corner and get to the upper part of the chamber, and then onto that big bridge.

When G'or flies up to you, start beating the tar out of him with missiles and don't let up. If you saved at least most of your missile inventory from the last level, you'll have enough without having to jump around gathering more. But there are loads of missiles in this level if you're running short. Also, on the corner ledge that was to your left when you first entered the chamber there's a Weapons Enhancement Chip (but not in Maniacal skill). With the homing-missile capability this provides, all you need to do is continually fire toward the general center of the chamber. If/whenever you don't have homing-missile capability, just get up fairly close so you won't miss much and keep pummeling him with missiles. His firing rate is pretty slow and it's not too huge a deal to dodge his fire. Try to stay on the bridge and you'll avoid injury from backsplash from his projectiles. You'll probably have to take a quick time-out to gather health. If you keep up a continual barrage of fire, you'll be done with him in less than a minute.

Indeed, it has ended
G'or is history. All that's left to do is destroy the Citadel and escape. Go to the main ledge: the door at the end is now open. Hit the switch inside to begin the auto-destruct, and board the escape pod when the hatch opens. Hit the switch and blow this joint, quite literally.