Cortana (level)/Walkthrough

General Walkthrough
The recommended active skulls on this mission are Tough Luck and Catch. Tough Luck doesn't have much of an effect since the room for the Flood to evade your grenades is limited. As for Catch, the Flood don't use grenades, so it's a consequence-free multiplier. Also, the Thuderstorm skull will have little effect, as flood have no ranks. If you gain 15,000 points, you will unlock the Orpheus achievement.

Also note that the Flood-infested High Charity has changed a lot since you were teleported there by the Gravemind in Halo 2. It is disturbingly easy to lose your way, so always pay attention. Beating this mission is a matter of measured progression, and the right weaponry is essential. The Brute Shot, Energy Sword, Shotgun, Plasma Rifle and Gravity Hammer are highly recommended weapons against the Flood here. The confined spaces make for several close-quarters battles, so good Melee weapons can always be useful. There are many irritating Ranged Forms that hang from the ceilings, so a medium to long-ranged firearm is also essential.

Shotguns are also very useful, but ammo is very limited. Use it until you make it to the crashed Pelican, get the ammo, and make sure you have an Assault Rifle, SMG, or Plasma Rifle to take care of swarming Infection Forms. Make sure to pick up the Flamethrower to incinerate anything in your way.

Search for Cortana
Drop down and fire upon the Infection Forms. Unless you're actively seeking a higher score, make sure they do not re-animate any of the nearby corpses. Replace your Assault Rifle with a Plasma Rifle and collect some grenades before moving on. Plasma-based weaponry is more effective against shielded Combat Forms, should you encounter any. Throughout this mission, take care not to shoot the Flood Growth Pods on the walls; they will release many Infection Forms if hit with anything other than a direct Flamethrower burst.

As you round the corner, a few Flood Growth Pods will automatically explode. Eliminate them quickly so that they don't re-animate any bodies. Head up the sloped path to reach the chamber's upper level. Find some grenades and grab a second Plasma Rifle to dual-wield with the first. Also replace your Shotgun with an Energy Sword.

When you reach the Porta in the floor, drop through it and immediately take cover in the corner behind you. After a moment or two, Combat Forms will move into the open. Blast them one-by-one with your Plasma Rifle, ducking back into cover if your shields are down or if your weapons have overheated. After the Combat Forms withdraw, Carrier Forms will start waddling towards you. Destroy them with grenades - Plasma and Incendiary Grenades work best. If you can find a Brute Shot around here, replace your Plasma Rifles with it.

Expect to find many Pure Forms and Combat Forms on top of the fleshy hill. The best tactic here is to dash over to the crashed Pelican straight away. The journey there could be a bit fraught, but you can find useful equipment there -- the Flamethrower in particular. Using the Flamethrower will make the battle much easier, especially on higher difficulties. If you're lucky, the Flood won't follow you as you flee to the Pelican. Camp there, luring Combat and Pure Forms towards you; the latter are easy prey for the Flamethrower.

Be cautious as you leave the Pelican. Pure Forms and Combat Forms might be still lurking around. Run to the other side of the hill, and make your way to the chamber exit. Note that a slope to the left of the portal leads to an upper level where you can acquire two Plasma Grenades and an Incendiary Grenade. The next corridor is empty, and easy to find your way through.

The room after that contains a small slope and several Infection Forms. The chamber is filled with dead Elites and Brutes, as well as some grenades; replenish your grenade supply, but first use short bursts of flame from the Flamethrower to stop the Infection Forms from taking advantage of the corpses in the room. You can throw a grenade to set off a chain reaction and weaken or kill any corpses that do get re-animated. In the next tunnel, grab either a Gravity Hammer or Energy Sword (your choice), and then drop through the hole to continue.

After you pass through the entrance, head straight to the left. This area provides cover from a group of Ranged Forms as you dismember the first wave of Combat Forms in close combat. Operate from here, drawing the Flood to your position.

Co-op Method
Another way to beat this mission would be to use a better player to escort you in Co-op. Follow them, and don't stop to kill anything -- just run to each checkpoint. Keep the Energy Sword handy if you run into some trouble but you can take whatever weapons you feel like (though you should probably let your more experienced friend have first pick). This only works on lower difficulty modes, though, and even then, you will still die a lot.

Introduction
Out of every campaign level in Halo 3, Cortana is usually judged as the hardest. The endless amounts of Flood that attack you and the limited amount of ammo you have determine the difficulty of this level, and on Legendary, it will be nearly impossible to tackle this task.

Many people have attempted to beat this level by actually fighting their way through the level - and as some may have completed it this way - it will be a challenge that only the best of the best can complete. Many people take a strategy that some call cheating, being lazy, etc. but it is by far the strategy that will provide the best results in the end.

This is called the "Running Man" strategy, where instead of fighting the Flood, you simply run as fast as you can through the whole level, and with a little luck, your life will be a lot easier.

MISSION START
When the level starts, you will spawn with a shotgun. This will be useful for a short while, but we will swap it out later. Progress through the infection forms running, don't waste your ammo on them. Once you get to the point were the combat forms spawn, throw a frag grenade at them and they should all be dead. Continue running, and then you should get to the point were you drop through the hole in the floor.

Once you enter here, you will be bombarded by Flood. I would actually fight these, because normally there is one with an energy sword, which will definitely come into use later on in the level. When the carrier forms attack you, throw a firebomb grenade and you will be able to skip the infection forms.

The next room is one of the most difficult places in the level, so be prepared to keep at it for awhile. First of all, when you get to the nav point a convoy of Flood will attempt to kill you. This is were the Running Man strategy comes into play. On the left wall, there is a Pelican on the ledge, and in this Pelican is both a Flamethrower and a Rocket Launcher. It is strongly recommended to swap out your shotgun for your rocket launcher, because it will be vital for completing this level.

Once you get your weapons, run as fast as you can through this room, jumping at every second and avoiding the flood at all costs. It may take awhile, but eventually you should reach the end. Near the end door, there are a few carrier forms, so be aware of the fact that if your shields are down they will kill you fast.

Once you get to the end, you get to a room with a few regenerating Flood. In the room somewhere there is a Brute Shot, so swap out your energy sword for the Brute Shot.

Once you drop through the hole in the floor, you will enter another difficult point of the level. There are loads of flood, mostly pure forms that change into ranged and tank forms, that will all be trying to take you down. For the ranged forms that stick to the walls, I recommend taking them out with a shot of your rocket launcher, and try to kill the tank forms with your Brute Shot.

Once you are able to hopefully get to the center of the room where the Tank Form is, there is what makes the level a vacation for you. Near the center of the room, there is a cloaking device, that allows you to skip through a part of the level undetected. Get this now, because the next part is going to be determined by how you use you rocket launcher and your cloaking.

Once you reach the thin hallway that leads to the room with the 2 carrier forms, be sure to take them out with your Brute Shot and destroy whatever else enters the room. Then, instead of running through the bottom where the flood have an advantage on you, there is a small ledge before you enter the room where you can actually got through the room on the roof, which give you an advantage.

First off, I hope you still have the cloaking, because you definitely need to switch it on here. There are endless amounts of combat forms that come out of the exit, and unless you attempt to take them all out with your rocket launcher, which is very possible, you will need your cloaking to survive, because there about eight other pure forms in the room, and are normally transformed into ranged forms.

Once you exit this room, check your ammo to make sure you aren't out. By now, you are nearly done with your rocket launcher, so if needed you could swap it out if on low or no ammo. As far as your Brute Shot, keep it for sure.

The next room is another annoying part, so be patient and prepared to be at it for awhile. First off, it is the same story as the last room, cloaking is necessary. In one of the narrow hallways there are two cloaking devices. First off, get one and use it to progress to the end of the room. For the second one, keep it for later.

Once you get near the door, your cloaking will wear out, so if your shields get down, definitely use the second cloaking. Run to the next door, and pick up the Brute Shot ammo next to the door.

After the long path to the area were you get to save Cortana, there are plenty of Flood there, but it is not nearly as difficult as the first challenging room.

When you get there you should be on a ledge with a few pure and combat forms, so try to take them down with your brute shot. When you get to the middle of the room, try to take some of the Flood down from range. There are lots of places for cover here, so use them when you are close to death. Then on the opposite end of the center tile, there is another cloaking on the right end. There is also a ranged form here, so strafe and jump to avoid being killed. When you get the cloaking, hurry to the door were you save Cortana.

When you reach Cortana, simply melee the glass globe that she is in and watch the cutscene.

After the cutscene, you will find yourself back in the same area you where in before. Now you have to work your way to the center tile and press the button that will open a few things that you have to blow up. While fighting off the Flood, get out your Brute Shot and shoot at the nav points on your screen. One shot should do just fine. If you get down on health, activate your cloaking.

After this, you have to run out of the room and in to the same room you where in before. If you notice, you are going in the same path you were to get to this area, but backwards instead of forward.

Once you get to the hole in the floor, take out the combat forms with your brute shot and stay on the top always. Just keep running and running, and try to kill all of the Flood in your way.

Once you finally get to the room were you got your first cloaking, try to take it slow and kill the Flood one at a time, because a lot of them have brute shots and shotguns, and they could kill you quickly.

Once you break through the wall of Flood, keep running and running, and eventually you will reach the first room that all of the Flood have attacked you in. If you listen, Cortana will mention something about a "friendly contact" and you will notice that the Arbiter has joined you, with a flamethrower. Just simply let him do the killing, and run past all of the Flood to the Pelican where you got your rocket launcher at. Go in the Pelicans troop bay and the mission will end.

Legendary Walkthrough
Cortana is probably the hardest level in any Halo campaign game. But it can be beaten by a good player. The secret is to make the most of what you have.


 * Know how to use every weapon to its greatest effect.
 * Unless you have beaten the level on lower difficulties, keep your MA5C, no matter what. You'll need its compass.  There really isn't any weapon that is weak in all situations.  The only exception is a Plasma Pistol overcharge—while it takes out Brute armor very effectively, it does little to the Flood.  If you get a Plasma Pistol, use normal shots.  The Flamethrower uses approximately the same amount of fuel for killing a Combat Form as for killing a Pure Form; therefore, save it to kill Pure Forms.  Human weapons provide an advantage if you are using a Deployable Cover in that you can remain where you are--safe--and fire on the enemy.  Spikers are particularly effective against Ranged Forms.  Don't hoard weapons continuously, despite how much you may think you need them--if you hoard too many, you will overload the map.  The most common result is that some weapons disappear or fall through the floor.  But if you are trying to beat the level with Iron or else with minimal death, hoarding weapons is your best bet, although it is time-consuming.


 * Know how to use grenades.
 * Try to use most of your grenades, but keep at least two stickies (anything that is not a Frag). These are particularly effective against Carrier Forms because they kill not only the Carrier Forms themselves, but also the Infection Forms inside them.  If you are having trouble killing something, say, a Pure Form in the large room near the halfway point, go ahead and throw a grenade.


 * Know how to use equipment.
 * If you are a Halo 1/2 veteran, you probably made it this far, with difficulty, without using equipment. But on Cortana, equipment becomes a necessity.  Deployable Covers are probably the best equipment; they do not self-destruct after a while, unlike any other equipment, and you can fire while protected if you are carrying a human weapon.  Note:  The Carbine cannot fire through Deployable Cover.  If you cannot find Deployable Cover, use a Bubble Shield, as lesser forms enter your shield, you can kill them without worrying about exposing yourself to Ranged Forms.  But when the timer goes out, you will be exposed.  The Cloaking is only good for speedruns.


 * Have good aim.
 * Conserving ammo is of course an issue, and killing enemies quickly has always been an issue. But there is now another penalty for missing:  you may hit a Flood Growth Pod and release Infection Forms as a result.  These can reanimate corpses that you have not yet destroyed, or they can finish you off after you take cover from several Ranged Forms.  Be sure all of your shots hit the enemies.

Skulls:


 * Iron
 * Not recommended due to the length and difficulty of this level. If you do use it, hoarding weapons will work well, although it will extend the time required to complete the level to several hours.


 * Black Eye
 * There are no Regenerators and many Ranged Forms. Not recommended.


 * Tough Luck
 * A consequence-free multiplier; the Flood don't dodge.


 * Catch
 * Activate this skull if you have it; the Flood don't use grenades, but they will drop more when they die, and will cause many deadly chain reactions if you throw a grenade near one.


 * Fog
 * You will be surrounded very easily. The least recommended skull.


 * Famine
 * Low enough ammo as it is. Not recommended.


 * Thunderstorm
 * Nearly consequence-free; a few more shielded Combat Forms are all that will result.


 * Tilt
 * Will decrease the damage Plasma Rifles, which are otherwise very useful. Not recommended.


 * Mythic
 * Will result in consumption of more ammo. Not recommended.

Part 1: Rampant
You start out with an Assault Rifle and a Shotgun. Advance through the first room; you will encounter weak resistance. Be sure to melee corpses when you have killed them, just in case you accidentally burst some Growth Pods.

The second room contains the first Pure Forms of the level, but not yet. Kill the Combat Forms, then walk up the ramp. At the top, you will aggro a CQB weapon Elite form and several Stalker Forms. Quickly kill the CQB-weapon wielding form and take its ammo if it does not involve taking chances. The stalkers will transform into Tank Forms in most cases; retreat to the ramp and pump rounds into them until they die. Sometimes they will convert into Ranged Forms--a few melees often will kill them. If it is unsafe to melee, a Plasma Rifle works well because it will kill a Ranged Form before it overheats as long as every shot fired hits and the rifle was not recently used. Stick the Carrier Forms (it is best if you use a different grenade type for each). Then deal with the rest of the Flood in this area. You will need most of the weapons you obtained and several grenades. Pick up the Deployable Cover, but keep it. The rest of this section is easy until the one-way drop. “Walk” all of the weapons in the area into the drop, then drop down. To walk weapons, continuously run and hold RB, momentarily releasing the button whenever you pick up one of your weapons. This takes some finesse, but you will quickly get used to it. But before you do this throughout the level, please read what I said about hoarding weapons.

Deal with the immediate Flood threat, then rush forward and set up your Deployable Cover. The best place for it is to the left of the weapon drop pod, angled 45 degrees to the left. Alternatively, fire from the intersection-room if you have gathered weapons from the previous section. Use your MA5C or another human weapon to take out the Pure Forms (you can shoot through the cover itself from your side). If the Flood gather into a tight group, save some ammo and throw a grenade. Run past the cover to the back; it is safe and has a few Plasma Rifles as well as another Deployable Cover. Pick off the Ranged Forms (use your binoculars to track them down). When they are all wasted, take note of the weapon cache below you because you will return to it several times. Run off the center of the cache; the path ahead leads off of this room slightly to the right of the wall you face. But before you do so, get the Tilt Skull if you would like.

Stick the Carrier Forms and the Ranged Form. Be careful with the Growth Pods. The next room is quite elongated and contains several Ranged Forms as well as Combat Forms. Look up and to the left—the arch is a good place to deploy your Cover. Pick off the Ranged Forms. When the Combat Forms show up, retreat while pumping rounds into them. Throughout your progress through this room, you will probably make several trips back to the cache in the last large room. You will also find two Deployable Covers there. Use grenades as necessary. After the room is clear, look to the right of the entrance; you will see a destroyed hallway with a panel blown off. Enter the service corridor and you will find an M7057 Flamethrower. For as long as you have it, save it for Pure Forms.

After this, go through the Porta into the next room. Burn any Stalker Forms you find, but when the Combat Forms show up, switch to your small arms. There is a tunnel structure to the right where you can take cover. Using a Carbine and a Spiker, kill all Flood in the room. First worry about immediate threats, then Stalker Forms, then Ranged Forms, and finally Combat Forms. There are three levels to this room, and you will have to make two jumps. Fortunately, you can make both with your Flamethrower. Continue through the next room with the bones (surprising, considering the fact that the Flood need calcium); there will be no resistance.

Enter the reactor room. Turn right and advance, burning any Pure Forms in your way. Kill all of them. If you were frugal with your Flamethrower, it should burn out sometime around now. Cross the reactor core, then go through the doors. You should see that the Flood infestation is quite limited in this area. Cortana will turn green and say, “This is UNSC AI Serial Number CTN 0452-9. I am a monument to all your sins.” Enter the Sanctum. Cortana is in the center—beat the barrier surrounding her until it fails (2 swings of an Energy Sword or 1 hit of a Grav Hammer).

Part 2: Nor Hell A Fury
Watch the cutscene, then return to the reactor room. A Bubble Shield will be useful here; kill the Tank Form to the left and the Ranged Forms to the right. If, instead, you have a Deployable Cover, place it so that it shields you against the Ranged Forms. A Tank Form's hit can quickly destroy Cover, but the Cover is immune to the Ranged Forms' projectiles. Similarly kill all of the other Flood in the area. Prioritize: first anything nearby using an Energy Sword, then any Pure Forms, and finally Combat Forms. Destroy the pylons (the nav points will help you).

Drop down into the earlier part of the level and kill any Flood you see while retreating. Continue through the level, generally the reverse of how you entered. You will encounter minor Flood resistance. When you get to the room where you first fought Pure Forms, look out and you will see a damaged Pelican. Run to the cockpit of the Pelican to complete the mission.