Quarantine Zone is the ninth playable level in Halo 2. It follows the direct ending to the Sacred Icon, as such your weapons will follow over with you if you are playing this continuously. However if you finished the previous level with a Rocket Launcher than you will start with a Sword, if you finished with a Carbine you will start with a Magnum. The aim of this level is to collect The Index.
Quarantine Zone is a campaign level that is featured in Halo 2. The mission takes place in Installation 5, you will take control of the Covenant's elite trooper, the Arbiter. As the Arbiter, this is the only level that features the ability to take control of human vehicles. The mission is fallowed by Gravemind, and to some individuals it is one of the hardest and longest level ever.
You will fight Flood, Forerunners and some UNSC marines. The Sputnik Skull can be gained in this level in the Legendary difficulty. This level won't be an easy mission, there is a lot happening, a lot of Flood in vehicles and enemies with rocket launchers. Using Vehicles in this level is essential, the Gondola is preferred.
This done on Normal Difficulty.
 Objects in Mirror Are Larger Than They Appear
If you are starting this level here, you will start with a Carbine and an Energy Sword. The best bet is to hop into a Ghost and let your fellow Elites take the Spectre and the other Ghost. Straight away an Enforcer and two Sentinels, head to the sides and flank them. Once dead proceed through the tunnel they came from.
The next fight, try doing a hit and run tactic hit the Enforcers and run away, try to keep the furthest one alive to help deal with the Flood. Then kill the Sentinels, once all of the Sentinels are dead head on ahead and start to fight the flood. Near the next door you need to go to there is a Scorpion, jump in that and start killing everything.Once all those enemies are dead, proceed through the tunnel.
 Healthy Competition
Once the doors open stay inside with the Scorpion, staying inside will protect you from the Enforcer's Rockets. Destroy The Flood and The Enforcer and proceed onwards. Once they are dead go outside and look right and wait for the Enforcer to get high enough and kill him, if you look ahead now there will be two Sentinels, kill them and move on. Be careful as Enforcers will be appearing through the vents until you get to the bottom, once at the bottom Flood will appear. The faster you can go through the door the less flood you will verse.
Once through the door, go down and take out the Wraith, ahead on towards the wraith in the far right corner. Killing all enemies getting there. On the first bridge you will see a flood on the cliff ahead, kill him before the Ghosts due to the fact he is holding a Rocket Launcher. Kill the remaining Flood and Ghosts and move on.
Killing that wraith in the top right corner, there will be ghosts and an Enforcer. Kill them and move over the bridge to the right. The next bit only kill the people that are in your way. Once the path is clear, go in the tunnel.
Once there you will see a Scorpion don't shot, get out of your vehicle at the top of the hill and wait until the Sentinels and Enforcers kill it, go Active Camouflage and get in it kill all the enemies and head across to the other side. Get out, go Camo and run straight into the door where you need to go.
Follow up in the corridor, slash all the dead flood so they do not came back to life and head to the end of the corridor. Now look across the map and active Camo running straight across the level avoiding everything.
Once you pass there you will get outside again. If you activate Camouflage and head to the left, don’t kill any sentinels and only kill flood that are in your way when Camou goes off. Head through the tunnel, be careful as there is a shotgun and rocket Launcher flood member. Head through that tunnel and once again turn Camouflage on, head straight ahead ducking at the first bridge. You will once come outside. You will see a lot of Flood driving vehicles be wary as there is another Rocket Launcher flood, a Gauss Warthog, a Scorpion and a Wraith not to mention 3 Ghosts. Once those are dead head through the tunnel. At the end of the tunnel a warthog will appear and a ghost. Either avoid them via Camouflage or blown them up, across the bridge a Phantom will drop of a Spectre. Head in over it and drive, it is important you drive as the AI will drive you into stupid battles against things you cannot beat. Travel past the wraith and keep going straight using wraiths as a reference point. You will get to the building with a Machine Gunner Flood drive past and to the middle of the tunnel, a door should open. Drive on through to the Gondola.
 Shooting Gallery
This bit is pretty simple, just keep fighting you way through the groups of flood, it is best to keep you sword as if they over whelm, you can swing away. Also keep close to your AI friends as they can be used as bait.
This is one of the more difficult missions in the game, simply because the sheer number of enemies can overwhelm you if you do not contain them.
In this mission you start off on yet another moving barge. When the barge reaches its end there will be several swarms of Flood creatures that attack you in waves. This is one of the more challenging stages and you will have to try to bottleneck the Flood.
They enter through a tube on the lowest level of the barge - kill the first wave of the flood then go to the lower level and look for the tube. When you've found the tube, move back up a bit so that you have a view of the area where the Flood will come out. This is your "Killing Area", where you will make sure the Flood cannot swarm the entire ship, otherwise they will overwhelm your allies and you.
The key here is to control them right at this entry point. The position you should be taking is slightly above the lower area where they enter, from there you can shoot them and also lob grenades into the lower area. As the Flood enter that area some tend to stand there a second or two, this is PERFECT opportunity to take them out with grenades. Make generous use of grenades, literally throwing them into the pit or into the tube itself every opportunity you get. If done correctly, you will kill them off as them come out and not give them a chance to swarm. If any escape your barrage of grenades use an Energy Sword to finish them off, but QUICKLY return to your original. Every so often, run down to the killing area to pick up additional grenades.
Using this strategy you should be able to kill off all the swarms of invaders with grenades and still be left with enough to continue your mission.
Be wary however, and note that Flood will attack until the mission is literally over and the barge stops moving completely (there are several stages where the barge is moving, so do not relax until your allies tell you to go retrieve the Sacred Icon.
 That odd, Familiar Feeling
This is also a simple section, just walk around the building until you see an entrance, slash at the flood remains on the floors so they cannot get up. Walk through the door and watch the cut scene.