You start in a dark and dusty room with steps on the far side. Check to the left of the steps to get 5000 PTAS and get "Our Plan" from the table at the top of the steps. It's pretty much just a summary of events so far from Saddler's point of view. Open the door on the left to start a cutscene. Ada and Krauser seem to be plotting against you, though Krauser is very suspicious of Ada.
You're now in a hallway with steps leading down. Follow the path to the corner to get find Shotgun Shells, then go back and take the steps down to the lower level, defeating a soldiers or two that may come through the door. Shoot the sparkling object in the skylight to the north to get an emerald. There is a Green Herb at the bottom of the stairs.
Go through the door and fight the soldiers among the the large furnaces. Watch for archers on the left and a soldier with a shield.
At the end of the aisle you can go three ways. To the right is a storeroom with 3000 PTAS and a Flash Grenade. To the left, at the top of some steps, is a small office with possibly a holdout soldier. Get Shotgun Shells from a desk and Rifle Ammo from a locker here. Go back and through the remaining door at the end of the aisle.
Go through a hall and the door at the end into a lager room with large turbines. Most fo the room is fenced off though. Grab the Shotgun Shells from thr floor and take the lift to the upper level.
Now it's time for QTE hell part 1. It's a long cutscene where you dual Krauser with knives. But every so often you have to do one of those button combos to do a saving move as the two of you alternately talk and fight. There are six of them strung together and they are randomized. After these there is a part where Krauser jumps on top of you and you must press first one button, then another quickly to push him off. There is a continue somewhere near the middle, so if you get close to then end you won't have to start over from the beginning.
Meanwhile there are a few revelations in the cutscene part. Krauser is another acquaintance of yours but you thought he was killed several years ago. He's the one who kidnapped Ashley in the first place, but it was a way of gaining Saddler's trust. His goal is to get in deep enough with Los Illuminados to get the "sample" for Umbrella Corp. Finally Ada appears and turns on Krauser. He does a superhuman jump to escape, so it appears he may be getting power from the parasites as well. Ada leaves and you get a call from Saddler. He says that now that you've met an "old friend" here, he's going to continue being a good host and introduce you to "it".
You were probably watching for button presses instead of what was happening in the fight, so chances are that you didn't notice that you went over a ledge at some point. So you're going to be really temped to climb the ladder here, but that just takes you back to where the fight starts. Instead, jump down to the floor and go through the door.
Now it's time for QTE hell part 2. You enter a room and an automatic door opens as you approach. This reveals a long hallway and as you step forward lasers are activated. You must pass a series of barriers and they get increasingly difficult.
First, there are three beams; wait for the horizontal beam to start upward and the two vertical ones to separate, then run through. Be sure not to touch the beams since they are instantly fatal.
Second, there are four beams; the pattern is more complicated this time so take a moment to learn it. Wait for the two horizontal beams to start upward and move when the diagonal beams go vertical.
Third, there is a bunch of horizontal lasers that come toward you and you must press the buttons on the screen to do a saving move.
Fourth, you approach some lasers that seem to be malfunctioning. You need to do one saving move when they come on suddenly and another when they come toward you.
You finally reach the end but it’s not safe to breath yet. When you press the button to unlock the door more lasers approach and you must press the buttons at the right moment, just before they reach you, to execute the saving move.
The button combo is always the same in this hall, which is fortunate because there would not be enough time to react if you needed to actually get the combo from the screen.
The next room seems to be Saddler's personal relaxation room. Get the Elegant Headdress by shooting the sparkling object from the beam across the ceiling, then get the Emerald from the throne. You can try sitting there if you want but nothing happens.
Go behind the throne and take the elevator.
You enter a tunnel with cement walls that turns to bare rock as you go down some steps. Get a Green Herb and an Emerald under the stairs. Continue down the passage to find the Merchant and a typewriter on the right. Pick up "Luis' Memo 4" here; Luis summarizes what he knows about Las Plagas, comparing them to social insects. He also regrets working for Saddler, but his thirst for knowledge blinded him to Saddler's evil nature.
Go into the cage behind the Merchant and get Magnum Ammo and a Red Herb. Then continue down the passage and through the door at the end.
There is another passage leading to a large, bottomless cavern. First check a storage area to the left to find a yellow herb. Now go on and collect ammo from the ground. You get a close-up of a set of cages hanging from the ceiling.
Continue for a bit a get another cutscene. You find the tracker you attached to Ashley on the ground. There is rumbling and a cave in, then you find yourself in one of the cages. A giant monster, Saddler’s “It”, appears.
As bosses go, this is perhaps the most difficult in the game. There are multiple phases to the battle.
At the start of the battle you're trapped in a confined space with the monster. You can't really damage it now, but you can drive it away temporarily. The most effective place to aim at is the monster's head, meaning it will make it back off faster. So give it some TMP or shotgun blasts to the face until it jumps. If may only jump to the top of one of the crates here in which case it can jump back down with you at any time. You could keep trying until it jump to the roof of the cage, but you're using up ammo doing that and since you're not really doing any damage it's a bit of a waste.
If the monster gets too close it will grab you and will do major or even fatal damage depending on how fast you can shake out of its grip. If the monster is on the roof then it will take a swipe at you from above once in a while and you must do a saving move to avoid being grabbed. If may also try to grab you from a distance while on the ground and, again, you must do a saving move or get grabbed.
You don't have much time to react in the first encounter so try tossing a Flash Grenade to slow it down a bit before firing.
With the monster temporarily out of the way you can get your bearings. You're in the middle aisle and there is a Green Herb behind and to the left which you should get as long as you're here. Your path to the next cage is blocked for the moment and you must activate two switches. Access to the switches is blocked by gates which are controlled by green buttons. To start, go north, get the Shotgun Shells on the right, then go west to the corner and look to the south to see the first green button. Shoot the button and the gate next to it will open revealing the first switch, so press it. You can use your knife on the button if you want to save ammo, but it's a bit pointless at this point in the game.
Go back to where you started and continue east to the next green button. Shoot to open the gate as before and continue to the northeast corner where the switch is on the left. When this switch is activated you have 30 seconds to reach the red door on the east end of the cage and go through. In this case you're only a few steps away so, barring interference from "it" you should have plenty of time. You can do the switches in either order but you'll want to do the one to the west first to save time when it's needed. The map is your friend when the timer is counting down, so check it and plan your route whenever you're not sure which way to go.
Now you have to do more or less the same thing with the next cage but it gets a bit more tricky. The good news is that the monster is still up on the roof and you can get your bearings right away. First pick up an Incendiary Grenade to the south, then go back and head east. You can either go left or right when you reach the junction, but there are shutters blocking both paths. As soon as you go a step or two in either direction, a shutter drops behind you blocking your way back to the start, so now you're trapped in a tight space with the monster. It's so close to you that your shotgun is probably the best choice for fending it off, and when you do you can start looking for the green buttons. They're both above eye level so you have to look around to find them.
We'll start by going south. Turn to the south and look to the upper right to see the button. (You may have shot it accidentally already in which case the shutter will already be open.) Just shoot it with your shotgun since you have it equipped; it's not the time to quibble about a wasted shell. Follow the passage to the southeast corner and activate the switch on the left. Now go back to the junction.
Face north and locate the green button on the right pillar in front of you. Shoot to open the gate and turn left to get to the northwest corner. Activate the switch to start the timer, but all you have to do is go east and south, grabbing the Hand Grenade at the corner, then go through the door.
The first switch in the third cage is just to the right as you enter; you don't even have to shoot a button. Activate it and the monster appears behind you, now sprouting a Plaga that has a head of its own. This second head is the monster's new weak spot so aim at it from now on. When you've gotten the monster to retreat you can start exploring. The switch opened a doorway into a covered path though the middle of the cage. Follow this east and south, but watch for the occasional swipe by the monster. Continue east, circling around to the left until you reach a gate which you can’t get past. There is a green button visible through the gate, so shoot it to open a shutter. This turns out to be all the way back near the start, so backtrack through the covered path, then north and east to the second switch. Press the button, and follow the route through the covered path a third time to get to the door at the east end, dodging the monster when possible.
When you open the last door a hook appears, press the action button to grab it while the monster looks on helplessly, then watch as it falls in the bottomless chasm while you are carried safely to the ledge to the east.
You might think it's time to relax but nope. Step forward a bit to get a short cutscene and learn that “it” is not as easy to kill as you thought. It crawls out of the pit and chases you onto a ledge where you have to fight him for real.
Get the 50000 PTAS drop. The gate near where you jumped from the cages opens when the monster is dead, so go back and take the door on the right (northeast).
Follow the tunnel to a ledge with some machinery. Get the Green Herb from under the stairs, then take the cable car back to the ledge where “it” first appeared. Get another Green Herb here. You can back track to save if you want but there's no reason to. Ride the cable car back and climb the ladder there.
You come out at the bottom of a cement bunker. Climb up the ledge and get Shotgun Shells from the table and a Hand Grenade from a cabinet. Then go outside.
Get the barrel on the right, then notice an encampment below the ledge you’re on. There are soldiers here but you can get most of them at once by shooting an exploding barrel next to them. Drop down and get two barrels behind the large tent. Get TMP ammo under some awnings on the other side, then go right and get a Yellow Herb. Check the fence further on to see your destination. Go into the tent, get two boxes there and drop into the hole.
You land in a tunnel. Get the barrel at the start and follow the tracks. Follow a side path to the right and find the Blue Stone of Treason. After this follow a side path to the left to get two boxes. At the end you'll find the Merchant and a typewriter. This is also the fifth and final venue for the Shooting Gallery. You won't be able to return here later so this is your last chance to finish it.
Get a barrel here and Krauser’s Note from the table; it's about his plans to get even with you and then kill Ada for betraying him.
Climb up the ladder to an area past the fence you couldn’t get past earlier. Get a barrel and continue through the door.
Follow the ledge, get the barrel on the left, and jump down into some ancient ruins. (From this point you you won't be able to get back to the shooting gallery so complete as much of as you're planning to first.)
Step forward a bit for a cutscene. He's a bit miffed that you and Ada seem to be working together. Just so you don't get any ideas about leaving without a fight, he explains that you'll need three insignias to get past the door and reach Ashley. Two of them are in the ruins but Krauser has the third and he's not about to just give it to you. So it's time have it out once and for all. This is a strange battle in that you seem to spend more time smack talking than fighting and it’s interrupted several times while you explore the area. When you’ve done enough damage to Krauser at one location he throws a flash grenade and disappears until you meet him at the next location.
- Round 1
- Krauser starts by attacking from across a trench either with machine gun or grenades fired by a bow. The walls and pillars offer a bit of protection but will soon be demolished so they don’t help a lot. If you’re lucky you can snipe Krauser before he shoots, but he will quickly relocate and try again if you miss. If you score a hit then lower your site so you can see where Krauser jumps to.
- When you do enough damage or reach the stairs at the end of the ledge, Krauser approaches to fight at close quarters. Prepare to dodge with a button combo if he gets close. You can also take a swipe at him with your knife which seems to do plenty of damage against Krauser. (This isn't true for most enemies, but you do get a bit of a clue in your conversation with Ada in Salazar's bedroom.) Krauser jumps very quickly so it’s difficult to hit him with a gun, but you can usually get a good shot after he attacks and backs away. Use a good weapon you can aim quickly; a magnum would ideal but you'll want to conserve its ammo.
Go through the door at the top of the steps into a house. (You can also do this before fighting Krauser; you would then take him on indoors.) Get a Green Herb and a box inside, then climb the ladder to get a Flash Grenade and a barrel on the roof. Go through the door to the north. (This is a continue point.)
- Round 2
- (You might not get this round.) Krauser pops out from behind the walls up ahead and attacks at close quarters. Use the same tactics as in the previous round.
Continue and pick up Shotgun Shells on the left. Go down the steps to get to the northwest corner of the area; there is a panel with missing pieces and you need to get them before you can open the door, just as Krauser told you. Get Handgun Ammo on the left.
Go back and when you reach a passage to the east you may hear Krauser’s weapon.
- Round 3
- Krauser pops up on the roof of the building at the end of the passage, try to snipe him there. This time the fight is mostly long range so use your rifle. You may have to do a saving move if he launches a grenade at you.
Continue east to a small building.
- Round 4
- (You might not get this round.) Krauser appears behind a corner as you go around the building. This is another close quarters fight.
Make a note of the gate in front of the house. There is a lever but it can't be reached at the moment.
Enter the building and get two barrels, but watch for two floating drones that appear at the windows. If they appear then avoid them for a bit by climbing the ladder, then fire at them through the hole when then come inside the building. If they don't appear then climb to the roof anyway. Get TMP Ammo and a Hand Grenade there.
Continue east, then north and get a Green Herb on the left. Go up some stairs to get the Piece of the Holy Beast, Panther. There is short cutscene where you try to talk Krauser down, but he is clearly gone insane with megalomania.
- Round 5
- The door to get back closes. Krauser alternately jumps up to a ledge to drop grenades and fire down on you, and jumps into the floor you’re on to fight close quarters. The TMP may work well to get him off the ledge. Krauser stops occasionally to taunt you and be ready to respond with the action button; this seems to make him mad enough to try to approach for close combat.
Get the Red Herb and Handgun Ammo here. Now locate the statue that rose from the floor when you drove Krauser away. Push this to the light colored square on the other side of the two small brick walls in the middle. You have to push it to the side first to get behind it, then you have to push the other way when it runs into one of the wall.
This uncovers two levers; one to open the way back and the other next to the building noted earlier. Go back and get to the second lever.
- Round 6
- This is basically a duplicate of Round 4
Open the gate and drop down at the ladder. Before going forward, take out the two crawling drones on the left. Get TMP Ammo and a Green Herb in the corner.
According to the map there are two ways to go now, a longer route to the left and a shortcut to the right. Either way you may run into floating and crawling drones. When you reach the southwest corner of this level go north through a tunnel, fighting more drones as they appear.
Turn right at the corner to get more taunting from Krauser, respond and fight more drones. Enter the base of the tower on the left and a gate closes behind you. Get the Yellow Herb and go up the stairs. Make note of the gated doorway at the top, then climb the ladder to the roof.
First cross the bridge to the east end and pick up the Magnum Ammo and a Green Herb; do this now because you may miss them later.
Pick up the Piece of the Holy Beast, Eagle from a ledge at the west end. There is a cutscene where Krauser arm mutates into something nasty, you then have to do a saving move. Now it's time for the final round.
When Krauser is down, grab his insignia, the Piece of the Holy Beast, Serpent. You can check his body if you want to get an epitaph of sorts.
Drop into the hole you came through and go west through the door that was shut on the way up. (The gate at the bottom of the stairs is still closed so don’t even try going that way.) Drop off the ledge and head to the northwest corner to place the keys in the panel, then go through the door that appears. Note, you must actually leave the area before the explosives go off, not just get to what you would think is a safe distance.