Walk all the way back to the comm station and activate the terminal. Dacher will deactivate the big maintenance fan behind you. Drop down the shaft.
You'll be prompted momentarily to kill the two mercs below you. With that done, look for another merc around the corner to the right, working on the equipment there. Kill him and activate the comm terminal.
Achievement Alert! Opening the cell doors by activating the comm terminal will unlock the Rebel Achievement.
You're trapped here for a moment. Run to the dark corner to the right of the door and hide there while the two merc-controlled drones sweep the room.
When the drones are in the middle of the room, blast both with the tranq gun and then stealth kill them to clear the way. Head out the door they came in through.
Bounty! Go straight through the door and grab Bounty Card 11 off the floor. Then turn left to find the next door.
As you open the next door, the door beside you will open on the left and a merc will step out. If you're using a gun, blast him. If not, kill him quickly.
Turn left and get through the door. Kill the other merc inside.
Bounty! Check the crates in this room for Bounty Card 41.
Activate one of the drone control stations.
When the drone drops, turn right and blast the two mercs there. Proceed up to the flashing gate along the left wall and shoot the blue lock above it. Then steer the drone into the fan to stop it. When prompted, use the control station to take control of another drone.
Go through the fan room and open one of the green doors ahead. You'll face a ton of mercs, but since you're using disposable drones, just do your best to not get killed right away. When you've killed enough of them, you'll get a message from Revas.
You'll now have to engage a mess of merc-controlled drones. They'll drop out behind you, so turn around and find a good place to hit them from. When you kill them all, Riddick will automatically disengage the machine.
Leave the drone control room and turn left. Look for a merc-controlled drone checking out bodies. Kill it and grab some weapons off the floor. Then head toward the area with the fan.
TIP: At the fan, after killing a nearby drone, look for a green door. It's directly across from the fan and leads to the Armory, where you can get more ammo and a nanomed cartridge.
Go past the fan to find a room with a ladder. Shoot the merc at the top before he sees you and climb up.
Stick to the upper level for the moment and stay hidden. If you follow the catwalk around, you'll see armored soldiers below you. Stay above them and move around to the hallway behind you. Be careful of the merc there.
Bounty! After killing that merc, you'll find Bounty Card 2 at the end of the catwalk.
With that done, you can go about clearing the mercs below you. One good strategy is to tranq them all before they see you, then shoot them while they're flopping on the ground. You'll have to deal with five or so this way, however.
Bounty! Clear the mercs, then follow the upper catwalk to the bend where it turns toward where you found the last bounty card. Proceed to the edge above the area with all the mercs below and look for a hangrail. Cross it and walk to the end of the hallway to find Bounty Card 5 to the right.
Note: As you return from this area, watch out for a merc patrol checking into your handiwork. There may be as many as four of them, in places including the other end of the hang rail, two below your current position, and one near all the bodies by the crates.
Blast those guys from your elevated position, but do so quickly or they'll convene on your position and knock you out of the ceiling. You'll want to take on the one across from you first if possible, because he's the most irritating. As soon as you start firing your Assault Rifle or Shotgun, the other mercs will come running and zero in on you.
When they're dead, proceed down the hall below you to the green door.
Head through the door marked "Gravity Generator" and you'll pass down a hallway before entering the generator proper. Go into stealth mode as you enter the room and creep around to the right to avoid being seen.
The generator is that big thing in the center of the room, and it will actually draw you toward it as you move closer to it on this walkway. That means you need to be careful what you do and where you fight, as you could be pulled off the edge.
There are a lot of enemies here. Your best bet probably is to pull out your assault rifle, find a good spot, and start laying into them. You'll kill the first two mercs pretty easily; more will flood over from the area to the left.
When you've dispatched them, grab their weapons (the new SMG) and sneak along the walkway toward the other side. Up ahead are three more mercs to kill.
Bounty! Clear the room and backtrack to the door you started at. Stand in front of it facing toward the gravity generator. Look left. Walk under the ceiling and look for a blue panel to the right, closer to the generator. It's set near the edge of the area. If you approach it from its left side, you'll see Bounty Card 22 hiding near the edge, behind it.
Proceed to the other end and the door there. Go through into a red-tinted hallway. You'll eventually come on mercs who essentially are waiting for you. Smoke them with whatever guns you've got.
After those three mercs are down, you'll see two more down by the door. Kill them quickly to minimize the damage you'll take. Then go through the door into Gravity Generator 2.
Bounty! Before doing anything else in this room, move to the right edge just beside the door. You'll see a thin piece of metal that you can inch along around the outside of the wall. Walk along it to the end to find Bounty Card 14.
Move left toward the wall that the mercs closed on you. Along the left wall is a hole in the floor that you can crawl through. At the other end, climb up and Riddick will automatically toss a merc off the side of the area.
Sneak into a good position for a firefight and open up on the remaining three mercs here. Kill them and head out the door at the end.
Be careful as you enter the next door. There are two mercs at the T-junction ahead and as you enter, they'll ambush you. Fall back and take cover outside the door and pick them off as they come after you.
Grab health from the nanomed machine, then turn right and go through the door. You'll enter another room with large red tubes and three mercs wandering around down around the corner. Use cover and shadows to sneak up and take them out from close range.
Continue through the door, where you'll face another large merc ambush. The big crate on the left provides some good cover from enemy fire. Before long, a large vent will open in the floor behind the merc position, effectively clearing them out. Sit tight until it seals itself, then proceed.
Guess what: Merc ambush through the next door. Use the doorframe as cover and mow them down before heading through.
Bounty! Look on the floor between crates on the right side of this hallway for Bounty Card 57.
Bounty! Through the next door, avoid the mercs with divided attention to the far right. Instead creep along the left wall to the area behind the red screen, then look for Bounty Card 26 in the right corner.
Now sneak around the corner toawrd the two white-clad merc scientist guys. If you're careful, you'll be able to creep up behind both and murder them easily. Activate the panel they were inspecting.
Go to the end of the walkway and hop into the drone assembly line. At the end, enter stealth mode and wait for the patrol to give you a chance to start assassinating them.
Avoid the lights if you can. If you're quick, you may be able to effectively use the Ulaks to thin out the three mercs here. If not, get the shotgun out and use the dark to your advantage, popping the two men on the move and then sneaking away from the last remaining merc. Use cover and darkness to your advantage.
Bust a hole in the windows to your left if they're not already broken, head through and climb over the crates. On the other side is another window, but breaking it will give away your position to the science mercs on the other side. Line them up and cap them from afar before they're aware of you.
Approach the tables and speak with Miles. He'll give you some good information. Afterward, you can shoot him to put him out of his misery if you so choose. Then shoot out the window to leave.
Bounty! Immediately on the other side of the window, turn left and jump the railing for Bounty Card 42.
Next you can inspect the immediate area. There's a vent hatch in this room, but ignore it for the moment. Instead, head into the hallway. Go left and kill two merc scientists, then head back to the right and sneak into a large room with two mercs on patrol.
Tranq and kill the two mercs. They're up the ramp from you, but they're easy pickings.
Bounty! At the bottom of the ramp, head to the back right corner of the room to find a small chamber with Bounty Card 37 in it.
You're done here. Backtrack to that vent and open it. On the other side, you'll come out behind several mercs. Kill them from cover if you can. Be aware that there are more behind the glass lining the left side of the room, and two more will come from your left, through an open door.
Bounty! In the room where you climbed out of the floor, walk down to the far end of the room with the glass on your left. Look around the back side of the crates to the right to find Bounty Card 13.
When you're in the clear, head through that door on the left. You can use a nanomed machine there, and you'll recognize the room where you found Miles.
Backtrack to the glass and clear out the mercs, then hop through. Follow it to the end and drop down to trigger a big fight with drones and mercs.
After the short cutscene, whirl around and take cover behind you. There are a couple of mercs up on the raised area ahead, as well as drones dropping into the room. Pull out the assault rifle, find cover and start mopping them up.
You'll kill six or seven drones, maybe more. They'll be merc-controlled, but you can use their weapons to make things easier on your ammo counter. Just keep shooting and watch for drones flanking you.
With the drones destroyed, hide in the shadows and move up to where you can shoot the mercs without them seeing you right away. They'll be easy to put down.
Now climb the crates beside the raised area, heal at the nanomed machine and press the console to get in touch with Dacher.
Turn around, take cover and snipe the merc that just opened the door at the far end of the room. Jump down.
Bounty! Before heading through the door to the hallway, check the ledge over the door for Bounty Card 8.
Head out into the hallway.
Boss Fight: Mech
As soon as you step into the hallway, you'll get a cutscene of Revas' mech showing up behind you. You can't fight it, so just run. The metal monster will chew you up from behind with its machine guns. There's little you can do about it.
To minimize the damage, hug the walls of the hallway and try to put crates between you and the mech. It's fast and will keep pretty good pace with you all the way to the waste disposal room (which you cleared earlier).
When you get to the room, race up the ramp and wait for the mech to step on the big mesh trap door in the center of the room. When it does, press the switch and the mech will fall. Then Riddick will go in after it.
Once in the room below, you'll be able to hide effectively from the mech. Bad news: It always has a good idea of where you are.
Give the machine a wide berth. If you get too close, it'll immediately zero in on you. If you try to approach from the side or back while it's stopped, you'll get a metal punch to the face.
Instead, do laps around the room, stopping to take cover behind various objects. Equip the assault rifle.
Each time you stop, find the mech. Zero a shot on the rider's exposed face.
Firing your gun immediately exposes you to the boss. If your cover is good, you should be able to sit tight for a couple seconds and weather a few shots. When the coast is clear (and before the mech gets too close, make a stealthy break for the next position.
If you need spare ammo, there are a few clips scattered around for the assault rifle. Continue the hit-and-run tactic and before long, the rider will die and the mech will be defeated.
Now the fun part. Approach the mech and you can ride it yourself.
Achievement Alert! You'll receive the Control a Mech Achievement just for donning this suit of armor.
Riding the mech leaves you close to unkillable. Leave the area and progress down the hall, smashing your way through the mercs trying to stop you.
At the end of the line, use the mech repair station to get rockets mounted on your left gun. Use Left Trigger to fire them.