This is how to beat Skedar Ruins on Agent Difficulty. As soon as you accept the mission, there is a cutscene. If you are into the storyline of Perfect Dark, I suggest you pay close attention to what Elvis says. After the cutscene, you begin the mission in a simple room with a spiked pillar on your right. For this mission, I also suggest using the Falcon 2 until the boss. It only takes 5-8 bullets to kill a normal Skedar, 1-2 shots for a baby Skedar. After leaving the first room, a Skedar will appear either on the right or left. (In my experience, it appears mostly on the right) After that Skedar is dead, continue around the corner. There will be another room with a Skedar wielding a Reaper (A Skedar rifle that shoots very fast and take quite a bit of damage) After you kill that Skedar from the doorway, enter the room, but be cautios of invisible Skedar (You cannot see them with the IR scanner, it only makes them brighter targets once they become visible) In that room, there is a cloaked Skedar on the far left side. It will appear as you approach the center of the room. After the Skedar are dead, walk up to the spikey black pillar. Most likely Joanna will say "This seems to be one of the special pillars." if she does, go to your weapon select menu and choose "Target Amplifier" Joanna will pull out a strange device. Attach the device on the pillar as if you are planting a remote mine on it. After placing the device, press 'A' to switch back to the Falcon 2, and continue to the next room. The room is shaped like a half-circle hallway with 2 cloaked Skedar. Once you are half-way through the room, a Skedar will either appear behind you, or in front of you. (You can tell when Skedar appear, because it makes a shield sound) After reaching near the end of the room, another Skedar will appear either in front of you or behind. Yet another Skedar will appear just after leaving the room. (If you use the R-Tracker, 3 yellow dots will appear on the rader, attach one "Target Amplifier" to all 3 of them. Just make SURE you are sticking the correct pillars) Continue down the hallway, when you enter the next hallway, there will be a Skedar on both sides of you. Kill them quick to avoid accidental death. The room down the hall to the right is likely to have a spacial pillar. Down the hall to the left, you have 2 ways to go, forward or right. Don't go forward unless you have tagged all three pillars. (After tagging all three pillars, they will explode) At the end of the forward path will be a cliff into a gorge, dont run around on the lower ledges too quickly, if you fall off into the black abyss, you die. If you are still looking over the gorge, back up to the hallway on your right, and run as fast as possible at the gorge, you will fly over it to the other side, then climb up the latter. After you drop down into the next room, there will be another Skedar. After killing it, there will be a hallway, go down it and turn left and shoot a Devastator grenade at the wall, it should blow up, giving you access to the mechanical section of the level. Don't linger too long in the mechanical halls, baby Skedar respawn every couple seconds. Right as you enter the mechanical section, there will be a hallway that leads to a door on the right, go through and kill the baby Skedar on the right. There will be a strange rock that you can push around. Next to teh pillar in that room, is a button, push the rock onto the button to activate the bridge and complete Objective B. The IR Scanners work very well in spotting the baby Skedar. After the bridge is a winding hall with more baby Skedar. in the next room, there will be two Skedar with Slayers. (Skedar Rocket Launcher) Kill them quick. Above the Slayer Skedar is a bridge, take that bridge to the next room. Upon entering a certain room, Joanna will say "Oh no! The Skedar army in suspended animation!" in that room you will have to kill 7 Skedar. (It is possible to hide in the Skedar's chambers) After that room is the boss room. If you used the Falcon 2 the whole way, the boss will be a sinch when you use the Callisto. Before entering the boss room, just open the door and shoot his shield to green, then enter. (If you do, the boss will start the battle by recharging his shield, while he's doing that, you can take a shot at the large statue behind him) You must destroy the four spikes on the sides first, then you can shoot the center one to beat the level.