Your goal for this level is to follow the Monitor around the spiraling floor plan up to the index access point. The index serves as a key to activate Halo’s defense systems and destroy the Flood.

You will enter the vast central room of the Library. Quickly turn to your left and take out the armed Flood Fighters to your left. Immediately whip around and open fire on the Fighters to your right. Often the Flood carriers will try to surprise you by hiding in a nice ambush spot. When you are preoccupied in battle, they will emerge. Try to take them out at a distance with your pistol before they go back into hiding. Keep a close eye on your shields. If you have to, run back into the doorway to avoid being surrounded by Flood spores while your shields recharge. Once all the large forms are gone (infection forms will keep appearing sporadically) follow the Monitor to the doorway on the left.

Once you walk into the entry hall to the next room, a group of Flood will literally come flying toward you. The second you see a Flood fighter jump from behind the unit ahead, throw a plasma grenade on the floor in front of you and back up. As soon as it goes off, toss another one in the doorway. Several more Fighters will appear and fly forward from the explosion. If any survive, mop them up with the shotgun. If you accidentally tag a fighter with a plasma grenade, blast him with your shotgun to stun him long enough for the grenade to go off; if he charges you, all bets are off. Step into the next room. Your presence will trigger a few small groups of Flood to jump from two ducts directly ahead. Back up into the central room and use grenades and the shotgun to clear them out, using the entryway as a choke point. Repeat this procedure until the ducts stop spewing Flood.

When you emerge into the next room, you’ll find it very similar to the first one you were in. Pull your pistol out and take out as many enemies as you can from a distance. Use a grenade or two. If you start to get swarmed, back up to the entry hall again, forcing the Flood into a single file line as you blast away at them. Watch your shields. If they gets low, back out and run around to avoid spores until your shields recharge. When the Fighters stop coming, go back in the room and scrounge around the floor for goodies. Switch to your pistol and move forward. When you reach the Monitor, a fighter on the outcropping to your right will open fire on you. Snipe him with your pistol before he gets a chance. Stand under the Monitor and wait for the large set of doors to open. Move through the doorway into the next room.

There is nothing but a cluster of spore forms waiting to the left, so take a right into the spacious hallway. On the floor ahead there will be three glass panes. Inevitably, the carriers will swarm the glass, shattering when they pop. Don’t forget about these three nasty holes, as you will be fighting around them soon. A group of Flood will appear around the glass. Shoot with your pistol and grenade them from a distance. Switch to shotgun when they get close. Always look for cover. There’s going to be a lot of shooting going on, so you aren’t going to want to be out in the open. The last thing you want to do is charge ahead full bore. Trigger one small group, back up, destroy them. Repeat. Repeat. Repeat. If you run out of shotgun shells, swap your gun for an assault rifle. It’s better than plasma and definitely better than nothing. When the large hall comes to a “T”, you will go left. A small group will come for you. Use grenades and pistols from a distance, shotgun at close range. Duck and cover.

Follow the large hall around until you see Guilty Spark again. A small group of Flood will pour from the duct ahead. Use grenades and backpedal around the corner to take cover while shooting. Around the corner to the right will be a health pack. A slot in the floor will have a super shield. Be advised that as soon as you round the corner a group will jump from the slot. Toss a grenade in front of the short ramp and trigger the Fighters right before it explodes to watch them soar. A few more Flood Fighters will appear before you can pick up the overshield but they shouldn’t give you too much grief. When the coast is clear, go down the short ramp and pick up the powerup. Overshields are a lifesaver when fighting the Flood. Since they are scarcer than bullets, you will want to open fire on the spores rather than letting them whittle down your overshield. Moving forward, you will trigger an ambush that will approach from in front and behind. Immediately back up to avoid getting swarmed and open fire on the Flood carrier closest to you. Take cover and fire at the Fighters as they come. Concentrate your efforts on the Carriers. Scoot forward slowly. Blips will appear ahead by another group of three glass panes on the floor. You can pretty much take out that group from a distance with your pistol. Once the coast is clear, creep past the fresh holes in the floor until you come to another bend in the hall. Turn right. Ahead another group of Flood will appear. However, there are enough walking pus pouches that you shouldn’t have much trouble eliminating them. Take the jog to the right past the library’s AV department and keep moving forward. Another group of Flood will appear, but this time a group of Sentinels will come to join the fight. Don’t feel too obligated to save them since they won’t follow you up the nearby elevator. Give them a hand, neutralize the threat, scavenge around for ammo and hop on the massive elevator platform at the far end of the hallway.

Wait, it gets worse!

Step off the elevator and head toward the doorway. To your right, a cluster of Carriers will drop. Blast them with your shotgun and step back to avoid their explosion. Head back in and go to the right. Sentinels will emerge from the alcove to your left. Move forward past the bank of 200” Jumbo-Tron screens and take the jog to the left. The Monitor will leave you and the sentinels to take out another small group of Carriers. Directly in front of you is another slot in the floor. This one has two health packs, so use one if you need it. Keep moving forward until you checkpoint. You will then get the infamous message: ”Hold your position until the Monitor returns.” Here’s where we have fun.

Go to the far end of the room next to another health pack on the floor. Toss a grenade into the nearest duct on your right. The Flood will begin pouring out of the ducts, so stay in that little alcove and let them come to you. Cream them with a little shotgun and ‘nade. When you get down to your last grenade, toss it in the middle of the room and run through to the opposite side of the room. You should pick up a few goodies along your way. Continue doing what you’ve been doing until the Monitor returns. Grab a health pack and follow him through the big doors.

This next room is the large circular room directly above the index. Whip out your pistol and follow 343 Guilty Spark. A large group of Flood will show up ahead. Toss grenades ahead of them and open fire on the Carriers behind. See how high you can make the Fighters fly. Repeat with the next group. Repeat with the third group, keeping an eye out for rockets. When the coast is clear, scan the floor for ammo. Resist the urge to pick up the rocket launcher; it will just mess you up due to the time it takes to line up a shot and switch back to a close range weapon. At the end of the room there will be another set of doors. You’ll also get another message to hold your position. Relax. This one’s easy. Go grab a rifle behind you and mop up the waves of spores as they come towards you. Shortly the Monitor will return and the doors will open. Clear away the popcorn forms, swap your weapon back and move through the doorway.

Follow 343GS to the right. Ahead will be another slot in the floor, but this time the descending ramp actually goes somewhere. Take out the small pocket of Flood resistance ahead and proceed down the narrow ramp. Pull out your pistol and pop the Carriers. Carefully peek around the corner ahead and pop the pregnant pusballs waiting for you there. Move forward down the narrow walkway until you see the exit. Several Flood forms will jump down. Back up and use the corner of the hall for cover. Toss grenades and use your pistol until the area is clear. Move up the ramp and out the exit. Spores will be there to hop down on you so make sure your shields are full. Follow the Monitor to the left. Stop right before the hall comes to a “T”. This AV corridor will have Flood attacking from both ends, so stay back and clear this hall like so many you have before. Once the waves of Flood dry up, move forward and follow the large hallway. When the Hall comes to a “T” again, pull out your pistol and turn right. At the far end will be a large group of Flood Carriers and a pair of rocket wielding Fighters. Stay back so you can dodge the rockets and start popping Carrier forms as fast as you can. When you've killed them all, move forward. A health pack will be in the corner to your left. If you need it, take it and follow the hall to the right. Another group will jump you. Fight them till they stop coming. If you feel compelled to pick up a rocket launcher, drop your pistol in a safe spot so you can pick it up immediately following this encounter. Follow the Monitor. An ambush will appear, but if you just keep moving forward to the elevator, you can avoid a fight altogether. Ride the elevator up.

But I don’t want to ride the elevator!

Hop off the elevator and turn left. You’ll come across a group of Sentinels fighting the Flood. Help them out if you want. Sometimes the Sentinels do more harm than good, though. Head down the ramp in another slot in the floor ahead. Follow the narrow hallway around. When you get to the turn, pull out your pistol and snipe the small group ahead. A large group of Infection forms will show up. Send them away with your shotgun. Lastly, at the next bend will be two Carrier forms. Toss a grenade around the corner or carefully snipe them from a distance with your pistol. When you reach the exit, a group of Flood and Sentinels will appear on your motion tracker. Back up and let them duke it out. When the blips on your motion tracker stop, proceed up the ramp. The Flood will have won and there will be plenty of survivors. Head back down the ramp and use it as a choke point, letting the Covenant funnel into your sights. When the area is clear, move up the ramp and into the room.

Turn right, pass the three consoles and turn right at the row of screens. Turn right again and follow the hall until it dead-ends. You’ll be asked to wait until the Monitor returns again, but this fight will be much easier than the first. There are just enough Carrier forms to make this a shotgun-only battle. There will be a health pack in the far corner when you are finished. Follow the Monitor through the doors when he returns. This will be the third floor of the index room. This time you’ll go clockwise around the perimeter. A group will initially attack from the left. Use your skillz and gunz to eliminate the threat and move on. The next group of Flood will drop onto the two tall blocks directly ahead. Stay back and use your pistol to snipe them before they can ream you. Move through the doorway into the next large, winding hallway.

A heath kit will be sitting on the floor ahead, should you need it. Follow the Monitor to the right. Switch to plasma grenades ad pistol. Stick a plasma grenade to the floor in front of the slot ahead. Three Flood forms will jump from the slot right about the time your grenade goes off. Pop the other forms with the pistol as they come towards you. Switch to your shotgun if any get in close range. The hallway ahead will come to a “T”. If you go forward, you’ll trigger groups of Flood on both ends of the “T” so back up and take them out, triggering one group at a time like you’ve done before. Take a left, left, right, right to the next set of large doors. Squeeze through the opening into the next room. Trigger the checkpoint and it will tell you to stay here until the Monitor returns. Slide into the niche between the outcropping and the double-doors and reload your shotgun. Don’t go too far back - just far enough to use the outcropping as cover. You won’t be able to stay here for long. Fight the Flood as best you can with grenades and shotgun shells. When your health gets low, use the health pack in the center of this room. Always reload as soon as there is a momentary lull in the action. You’ll end up having to use plasma grenades to supplement your arsenal. Try to hit the ground as best as you can. If you start getting surrounded, move to the niche on the other end of the room, picking up grenades on your way.

Once the doors open, several Sentinels will come to your rescue. Go out the doors and follow the hall to the left. Hang back and help your Sentinels fight the next group of Flood by using your pistol at a distance. Follow the hallway around to the end where you will get to the elevator again. Beware kamikaze Carriers that will drop from the ceiling as you go by.

Fourth Floor: Tools, Guns, Keys to Super Weapons.

As you get off the elevator, a few Flood Carriers will drop from above. Be watchful and get away if one gets next to you and prepares for self-detonation. There’s a health pack right here in case you need it. Follow the path to the adjacent bank of video screens where the hall comes to a “T”. Does this sound familiar? Go forward, trigger each wave and pull back to take cover behind an outcropping, letting the flood funnel to you at a trickle. Repeat this process again until they stop coming. Move down the hallway. You’ll eventually come to another slot in the floor with a ramp leading down to a small tunnel. Does this sound familiar? Head into the tunnel. Around the first bend will be a Carrier or two with a large swarm of infection forms. Pop them and proceed. There will be a couple more around the next bend. Pop them and proceed. If the Flood weren’t so much fun to blow away, this might actually get monotonous. Proceed forward up the ramp and take an immediate right. Although it doesn’t say so in your objectives, this will be another one of those “wait for the Monitor to return” moments. Stay in the niche on the right. If you go to the far left side, fighters will pour out of the opening above and on top of you. Besides, on the right there is a health pack available when you need it. There's another one on the other side of the door, so don’t feel obligated to save it for later. When the Monitor returns, move through the open doors and out. The health pack is in the floor slot ahead. Move forward; we’re almost there. Eventually, you’ll trigger the next wave of Flood. However, there won’t be an easy fall-back position. At this point, you need to just run and gun. Blast through the Flood quickly and get your butt out of there. Eventually you’ll come to a large pair of doors on your left. This is not a good place to turn and stand your ground. The Monitor will come and open them, allowing another wave to pour in from behind. Keep moving and duck in the first niche past the door. THIS is where you will make your stand. Use plenty of grenades and blow away anything that moves. When the coast is clear, move toward the open doors.

Ahead, you will see the central elevator that rides an energy beam down to the index. Although it may look clear, don’t be fooled. There is a massive flock of frikkin’ Flood waiting on the sides to flank you, fire at you, and flog you. Before proceeding, scavenge around until you have a healthy supply of grenades. When you're ready, creep towards the doors. If you’re quiet, you can run about halfway to the elevator before being detected. If you have full health you might just make it. If that isn’t working, then you’ll have to eliminate the threat as best as you can. Hang back as far as you can and snipe the Fighters standing on the left pillar. Then turn and snipe the ones on the pillar to the right of the doorway. If they aren’t visible, shoot the wall near them to get their attention. Hopefully you can take out the doorway guardians without alerting the rest of the crowd. When they are taken out, run through the doorway, making a beeline for the elevator. When you start taking fire, do a 180º and blast away with your shotgun while backpedaling to the elevator. Eventually, the cutscene will kick in. When all is said and done, passing this level requires not only a little knowledge, but also a lot of skills and some plain old dumb luck. Good luck.