You begin this level with a waiting ambush and a tough fight, but the rest of the level is one of the less-involved experiences in the game. When you move forward into the room ahead, the walls open to reveal a larger surrounding room with many more enemies. (This is a good place to set off a Death Sphere.) When you have everything cleared out, go to the next room. The door ahead is the exit; the door to the right opens from the other side. Follow the passage left down to the bio-muck and continue down through a large flooded room with a bridge overhead.
(On the way, in that confluence with the column in the middle and two blocked channels, you'll see an alcove high above where you came into here, well out of reach. It's inaccessible in single-player gameplay but there's a deathmatch spawn-point there. The two items are a full-health and 4 Evil Li'l Buddy Cells, if you were to use the \DIG cheat to go up there and look.)
On the other side of the room with the bridge there's a T-junction. The main way is to the left, but go right first. This goes to a large, tall room filled with bio-muck, with several Mazrium platforms overhead you'll get to later. Get rid of all the enemies now, that way you don't have to deal with them while crossing the platforms. The lift on the right is powered down right now, but will work later.
Biogen mixers[edit]
Now go back to the T-junction and continue that direction. Just past it are two glassed-in tubes set into the walls on either side. (The glass may have been broken while fighting enemies here earlier.) You'll see a gap near the floor inside the right-hand one. Activate the back wall for a secret area containing a Secret Level Access Keycard. Hit the switch in the next room to power a door just down the corridor. Continue down the corridor, past another of those big green bio-chambers, through the door and to the room on your right. In here is the first of three biogen mixers you need to shut off. Hit the switch to turn this one off, and continue up the corridor outside, over the bridge and to the tall room with the Mazrium platforms.
Use the Mazrium platforms to get to the other side of the room. You'll be under attack by enemies in that overlooking side room. This is a good time to use homing missiles--you should have picked up a Weapon Enhancement Chip just outside. If you fall, the lift is now powered up; manually activate it to lower it. On the other side, hit the switch to unlock the door, and continue from here. Go into the overlooking room on your left and shut down the second biogen mixer.
Long channel[edit]
Follow the main corridor to the end. You'll be at the beginning of a very long, tall, meandering bio-muck channel with a string of Mazrium platforms you'll need to use to get to the far end. It might be easier to jump down to the bio-muck first and waste all the Gryklaan and wall emplacements along the channel before going back and riding the platforms. Around the corner there's a bridge and a ledge. Jump up to here, and activate the centermost section of wall on the ledge for a secret area. At the end of the channel, jump from the platform to the ledge before it goes up into the hole in the ceiling. (But there's no harm in riding the platforms up into the hole, other than you might have to go back and ride a platform from the beginning. Give it a try if you want. As an aside, this would have been a great place for a secret area.)
Take the lift from the ledge up to the last biogen-mixer room and shut off the mixer. This unlocks the door, which goes back to the room where the level exit is. Your tasks are now completed here. Take the exit elevator to continue your mission.