Quake II/Lower Palace

Level objective
The main objective for this level is to first fight your way to the Upper Palace where you will find the Data Communications Laser CD and bring it back here, then to re-program the Data Spinner that you brought from the Outer Courts and finally to take the re-programmed Data Spinner back to the Upper Palace. A secondary and optional objective is to locate the basement-level entrance to the Upper Palace.

Strategy
In this level, there are several situations where Strogg appear unexpectedly above or behind you, either because you can't look in every direction at once or because the genuinely weren't there before. This is made clear in the Walkthrough, below, but if you're not going to follow that just be constantly on your guard and ready to duck behind cover of some sort.

Walkthrough
There are two entrances to this level from the previous level, the Outer Courts. This walkthrough assumes that you are first entering from the water / sewer area and already have the Data Spinner.

Part 1 - Getting to the Upper Palace
You will enter the level at the bottom of a ramp leading up to a low room with exploding barrels in it. In the room are a few Guards and Berserkers. Shooting the barrels is a good start. Some of the enemies are on a balcony over the your head. Both shooting from cover and charging out with guns blazing will work here. (See Secrets, below, for a secret that is accessed from this room.) Leave this room through the only door and follow the only available path, taking care of some Guards and a Brain along the way, until you come to a door on your right that is outlined in yellow lights. Just before it, a section of the floor is outlined in red and grey stripes. Beyond the door is an alcove. As you advance past the alcove, you will be attacked by Guards coming around the corner ahead and to the right. But, at the same time the floor section behind you will explode and one or more Technicians will come up from under it. Take out the Guards quickly and turn to take out the Technicians. The alcove will give you some cover. An effective, if slightly unfair, tactic is to send a grenade around the corner before the Guards even appear and then walk backwards, facing the Technicians as they emerge.

Turn left at the corner where the Guards came from the right. Ahead will be a doorway outlined in red lights and blocked by a force field. The Guards and a Tank behind it cannot hurt you ... yet. You can probably get a little in-fighting going. Deal with the Guards, Brains and Technician in the room to the left of the doorway. In that room you will find a security console emitting sparks. Ignore the sparks and press the button. You will receive the message "Red Force Fields Deactivated". Now take care of whatever is left behind the doorway. (Where have you recently seen another area blocked by a force field and outlined in red lights? Could it be in the Outer Courts?)  As you go through the doorway, look out for Berserkers and retreat if necessary while you destroy them. Follow the hallway and you will meet a Tank, some Guards and a Berserker, all facing away from you, expecting you to be coming from the main entrance. When you arrive at a blue disk on the floor with red carpets leading forward and to the right, the other entrance from the Outer Courts is to the right. By all means check it out, but remember that there were Tanks on the stairs and they will still be there if you didn't take them out earlier. (See also Secrets, below.)

Continue straight ahead and around to the left, dealing with the Berserkers and Tank that block your path. You will come to wide, ornate doors that open to a landing half way up a large, high, very ornate room which houses a computer console on the ground floor below you. There are Technicians floating around, Guards and a Brain below and Berserkers waiting to rush out of the doors to the right and left. Take down the Technicians first, keeping away from the doors. Then peek through the door around to the left-hand side and take out the Berserker in there. The Berserker behind the right-hand door might get aggravated at this and come after you; otherwise, just keep a lookout for him as the battle progresses. Deal with the Guards and the Brain below, maybe using a few grenades. Keep your eye on the balcony high up and across from the landing where you entered. If any Strogg appear there, a few rockets are in order; otherwise, if they stay on the other side of the balcony door, you will be dealing with them later. When the room is clear, follow the red carpet to the door that was to the left when you came into the room. Continue through the hallways and take out the Tank, but turn each corner carefully as you will arrive at a section protected by automatic blasters. There is a glowing button above them that you can shoot to bring up a barrier so that you can pass without injury (see also Secrets, below). Beyond this section of the hallway, take great care. The red carpet leads up some steps to a room in which there is a Technician, a Berserker, some Guards and a Tank. Because you can't safely retreat into the area covered by the automatic blasters (or, can you?), you need to stand your ground and take some damage while you clear up here. When you advance into the room, there will be another Technican waiting around a corner to the right. Some of these enemies may not show up if they came out on to the balcony earlier and you dealt with them there. You can explore the balcony by taking the stairs to the right and around behind the elevator (see also Secrets, below).

The red carpet has brought you to an elevator shaft. Press the button to call the elevator, step on and ride it up to an entrance to the Upper Palace. You will return to this level later, see Part 2, below.

Part 2 - Reprogramming the Data Spinner
Return from the Upper Palace via the elevator and follow the red carpet back to the landing in the computer room. Expect to find some newly arrived enemies; Berserkers in the hallway guarded by the automatic blasters, Technicians high up in the computer room and Tanks, one on the high balcony and one at ground level. Deal with these as you go and where you have good cover. Cross the landing, stepping off the red carpet, and turn left to the door on the other side. Deal with the Tank behind the door. The hallway will lead down to the ground level of the computer room, where you can access the computer. Go to the left-hand screen to deposit the Data Spinner, then the right-hand screen to deposit the Data CD, then finally the center console to get back the now reprogrammed Data Spinner.

At this point, you can return to the Upper Palace and complete the main objective of this unit. However, some of this level remains unexplored, so see also Part 3, below. Take the door through which you entered, which is to the right as you step down from the computer. Retrace your steps to the red carpet and follow it back to the elevator. Again, call the elevator down, take it up and go through the doors to the Upper Palace. No new Strogg will challenge you, but watch out for any that you ran away from rather than killing earlier.

Part 3 - Finding the Basement-Level Entrance to the Upper Palace
After reprogramming the Data Spinner and stepping away from the computer, instead of turning to the right and leaving the way you came, turn instead to the left and go through the door. You will find two Brains. Explore this small area and you'll find a room with a security console that turns off the force fields in doorways outlined by yellow lights (confusingly, this is not the yellow force field). Here also is a Brain. Press the button in the room (see also Secrets, below). A door around the corner from this room leads to the second, basement-level entrance to the Upper Palace. You will need to use this entrance to complete the Security Pass / Yellow Force Fields secondary objective of the Upper Palace level. Go through now, or complete the exploration of this level first (see Part 4, below) or take the Data Spinner to the Upper Palace and come back later. Just remember that the largest part of the Upper Palace can only be accessed through this entrance, even though you can complete the level and the unit and move on to the Inner Chamber and Final Showdown without doing any of this.

Part 4 - Completing the Exploration
Apart from the Secrets (see below), there is only minor exploration remaining and a few items to be picked up thereby. Note that a number of Strogg are hidden in one of the secret areas.

If you went to find the basement-level entrance to the Upper Palace, backtrack to the computer room. At the bottom of a ramp is a door that was previously blocked. It will now open, but there is nothing interesting on the other side. This is just the door with yellow lights that you passed by when you first entered the level (in this walkthrough).

At the intersection with the blue disk on the floor, where the paths from the two entrances from the Outer Courts combine, look out for a Technician that has appeared since you were last there. Crouch and drop off the edge of the walkway behind the pillar. Press a button to open a grating, crawl through and return to previously explored areas through a doorway guarded by lasers. Wait until the vertical lasers are on and walk in between them. Turn left and go to the end of the hallway and into the room with two crates. Climb the crates and jump up onto a ledge over the opening for Health and Rockets. Around the corner is the door to the ramp into the computer room.

Secrets
This level has six (6) secrets:
 * 1) If you come into the Lower Palace through the "back" entrance from the Outer Courts (through the sewers /  water) you will come up a ramp into a small room with a balcony above and behind you (from which Strogg will attack you).  To the right of the balcony, as you look at it from below, there is a section of wall that can be broken by shooting it.  It may already be broken from the firefight with the Strogg.  Go through the opening to find all manner of good stuff in several locations.  There is an automatic blaster that you can avoid just by careful timing.  Note also that there are Guards and Berserkers in there looking after the stuff.  Keep going until you collect an Invulnerability, then backtrack to come out of a hidden panel in the wall of the main corridors.  Because a) you may want to re-supply after fighting the Strogg in this level and b) popping out of the hidden panel doesn't put you in the best position to fight the Strogg there, you might consider leaving this secret for later on.
 * 2) After you collect the Invulnerability in the first secret and turn to go back, you will see an alcove full of all sorts of good stuff, but barred by a force field.  The opening is outlined in white lights.  To turn off this force field, you need to find the Security Pass in the Upper Palace, use it to enter the force field control room, also in the Upper Palace, and turn off the yellow force field.  Then you will have to come back here.  Note that there is some confusion about force field colors here.  The lights around a door do not always match the force field color.
 * 3) If you come into the Lower Palace through the "main" entrance from the Outer Courts, you will quickly arrive at a "T" intersection where there is a tall pillar of translucent material with a Quad Damage on top.  To lower the pillar and collect the Quad Damage, and the secret, shoot the face on the wall behind it, then turn 180 degrees and shoot the face high above where you came in.  If you get to the Lower Palace the "back" way, through the sewers / water, then you will come to this intersection from the side, so the faces are to the left and right.
 * 4) On either side of the cathedral-like computer room, there are doors leading to staircases.  The left-hand one goes upwards and to a room from which you can take an elevator up to one of the exits to the Upper Palace.  On the way, you will pass through a hallway protected by an automatic blaster.  On the wall as you approach there is a block that is not quite level with the rest of the wall.  Shoot it to shut down the blaster for good.
 * 5) In the room with the elevator to the Upper Palace, a staircase winds behind the elevator to the balcony of the computer room.  On the wall by this staircase is a diagram or computer screen.  Shoot it to open a secret passage.
 * 6) In the room with the security console that turns off the force fields in doorways outlined by yellow lights, the wall panel directly opposite the entrance can be pressed back.  This opens a secret room off the hallway outside, so explore quickly or it will close again.  There is, however, a button inside that will let you out, so you can't get trapped.