Cleanse High Charity. Save Cortana.

Starting Weapons Edit

Player V
Starting Point >
Mission Start Rally Point Alpha Mission Start
Rally Point Alpha
John-117 Primary Weapon
M90A Close Assault Weapon System M90A Close Assault Weapon System N/A N/A
Master Chief Secondary Weapon
MA5C Assault Rifle MA5C Assault Rifle N/A N/A
Master Chief grenades
Master Chief Primary Weapon
M90A Close Assault Weapon System M90A Close Assault Weapon System M90A Close Assault Weapon System M90A Close Assault Weapon System
Master Chief Secondary Weapon
MA5C Assault Rifle MA5C Assault Rifle MA5C Assault Rifle MA5C Assault Rifle
Master Chief grenades
2 M9 High-Explosive Dual-Purpose grenade 2 M9 High-Explosive Dual-Purpose grenade N/A N/A
Thel 'Vadam Primary Weapon
N'tho 'Sraom Primary Weapon
Usze 'Taham Primary Weapon

Type-1 Energy Weapon/Sword

Type-1 Energy Weapon/Sword Type-1 Energy Weapon/Sword Type-1 Energy Weapon/Sword
Thel 'Vadam Secondary Weapon
N'tho 'Sraom Secondary Weapon
Usze 'Taham Secondary Weapon
Type-25 Directed Energy Rifle Type-25 Directed Energy Rifle Type-25 Directed Energy Rifle Type-25 Directed Energy Rifle
Thel 'Vadam grenades
N'tho 'Sraom grenades
Usze 'Taham grenades
2 Type-1 Antipersonnel grenade 2 Type-1 Antipersonnel grenade N/A N/A


This is a walkthrough for the level Cortana, structured for play on Legendary difficulty with notes for lower difficultiy levels. Cortana is the penultimate level of Halo 3, and arguably one of the most difficult of the franchise. Your mission as stated is to find Cortana on the High Charity, free her from the Gravemind and eliminate the Flood.

Your most valuable pieces of equipment in this level are Deployable Covers and Bubble Shields. Cloaking is also handy but extremely rare. It is recommended that you always have a Deployable Cover with you. Grenades are also your friends here; Plasma grenades are very effective against Flood Ranged Forms and Flood Carrier Forms, and Fragmentation grenades will thin out large groups of Flood and bring down shields on the Elite Combat Forms. Most of the Combat Forms on this level are either Brutes are Elites, with very few Human forms appearing in the level.

Beware, though: if you have bad aim, you will be penalized in this level. Flood Growth Pods line High Charity's walls and if you are inaccurate you will unleash torrents of Flood Infection Forms that will make you waste valuable ammunition and probably kill you. Once you've killed all the Flood Combat Forms in the room, destroy their bodies so the Infection Forms will be unable to revive them.

Using Skulls on this level is not a good idea for inexperienced players, but using the Catch skull provides you with a distinct advantage, as the Flood do not use grenades, but upon death, they will almost always provide them with this skull active.

If using Co-op, the Arbiter starts off with an Energy Sword and Carbine. This is perfect because even when the Arbiter dies, he will respawn with these weapons, perfect for any use, including for dealing with the Pure Forms and Combat Forms that are highly abundant in this level. If John-117 dies on Co-op, he will start with a fully loaded Assault Rifle and Shotgun.

Part 1: RampantEdit

Entering High CharityEdit

You will start this mission with the M90 Shotgun and the MA5C Assault Rifle, though on Heroic it's possible to start with a Type-25 Directed Energy Pistol. At the mission start, use your Assault Rifle to clean out the Infection Forms. Make sure they do not re-animate any of the nearby corpses (a Brute and Elite). Search the corpses for a Brute Spiker, Plasma Rifle, and a Plasma and Incendiary grenade. If one has spawned with the plasma pistol, take the Spiker to get some added firepower.

As you round the corner, there's a fork. Take the right path. As you go reach the top, the pods explode, releasing Infection forms that will infect the bodies of Elites and Brutes alike. Using the right path gives a minor advantage, as this avoids being unexpectedly being ambushed by Elite Combat forms from the top, although you need to deal with them because the Infection forms immediately infect several corpses when you reach the top. Once all the Flood are dead, search the area carefully for any grenades, provided that they haven't blown up to accidental firing. Swap your Shotgun for the Energy Sword.

When you reach the porta in the floor, drop through it and immediately take cover in the corner behind you. Stay sharp because several Combat Forms will appear. Take them down with quick bursts from your Assault Rifle, then close in on them and finish them off with the Energy Sword. Back away slowly and look out for the Carrier Forms that will appear. Use a grenade that sticks (Plasma, Spike or Incendiary) to kill them. When stuck with a grenade, Carrier Forms do not unleash Infection Forms.

The PelicanEdit

For the next area you'll want to be quick. Follow the path up and around. You should see a couple of Deployable Covers here. Grab one and make your way to the large opening in the wall, leading outside the High Charity. There are many Combat Forms here as well as Stalker Forms that like to become Ranged Forms. Load up on ammunition here at the Pelican and get ready to move. You can grab the Flamethrower here. It can be a great help on lower difficulties, but on Legendary difficulty it is best to leave it: you will probably end up getting killed by burning Flood forms. If you choose to leave it here, it will greatly help at the end of the level (which is at the Pelican).

From here you have a choice, you can set up your Deployable Cover and shoot out the Combat and Ranged forms, or you can run past them. You're going to need as much ammunition as possible, so while you could clean out this area (and if you're playing the Meta-Game for points you should) you're much better off just running back inside, going to the left, and making your way to the porta and to the next area. The Flood will not follow you once the porta closes.

If you used any plasma/incendiary grenades, before leaving the large room, turn left to a path where there are some Elite and Brute corpses. There are several plasma/incendiary grenades near them.

Keep moving to the next porta, where a Cortana/Gravemind memory appears. Keep moving to find a slope with bodies of Elites and Brutes. Infection forms will appear, and they tend to infect the Brutes because of the distance from them and the Elites. Alternatively, because of the grenades in the area, you can set off a chain reaction by throwing a grenade of your choice, which should kill most of the Infection Forms. Deal with the stragglers afterwards.

Scan the area closely, as there are powerful weapons not to be missed, such as the Gravity Hammer, Brute Shots and Energy Swords. There's also a Plasma Pistol which you can use the "Noob Combo" to kill the Elite Combat Forms that appear later on. Use the weapon hopping method to drop weapons into the open hole below that leads to the Terminal Room as there is no going back when you drop down into the hole. Don't drop too much weapons down though, or the game will overload and delete some of them.

The Terminal RoomEdit

You'll be in small enclosure. Throw your Deployable cover as fast as you can, as many Ranged forms tend to attack as soon as you drop down. The Combat forms tend to walk slowly toward you, so shoot them down quickly or face a quick death. A dead Elite is nearby with a fully charged Energy Sword. As the Tank forms appear, lunge at their "mouths." Stick any visible Ranged forms with your Plasma grenades. As you near the end of the room, multiple Tank forms will appear. Deal with them one at a time (unless you're on Normal or Easy). Then keep moving up as until you reach a specific point, as if you clear the whole room you will still get a swarm of Infection Forms coming in through the way. Although they don't infect corpses, they will try to attack the player, which can be annoying on harder difficulties. 

Before leaving the area, you may want to familiarize yourself with the area. There are various lockers, and in the room containing the terminal, there are various equipment, including another Gravity Hammer, Maulers, Cloaking, and grenades. There are a few lockers containing Plasma Rifles/Pistols and Needlers.

When you keep moving, a few Carriers will appear. DO NOT throw your Plasma or Stick grenades yet; doing so will make them burst, and the grenade's explosion will release even more Infection Forms from the pods. Make them get closer to you (make sure there's none or little pods nearby) before killing them. Now keep moving and you'll be in a long narrow alley. There are plenty of Ranged Forms in this area. A Needler can help in this area as enough spikes on them will kill them quickly and efficiently. 

As you proceed, midway through some Combat Forms will appear. As you reach the end of the area, a squad of Combat and Tank Forms will appear. You can use your Cloaking if you want, as the Combat Forms are all equipped with weapons and you certainly don't want to be dealing with them in an enclosed area. More Cloaking can be obtained further on.

The Spiral RoomEdit

When you get through, another hard part appears. You have a similar amount of Ranged forms, and slightly more Combat Forms. Grab a Carbine from the ammo locker and try to headshot the Combat Forms, as they will be your main threat when in cover. Grab grenades and deal with the Ranged forms one at a time. Jumping may be required in some places. When you clear the room of foes, search the area for more supplies, including some Cloaking.

The Reactor RoomEdit

When you see the last porta open, turn on your Cloaking. If you feel you won't be able to get past in time, kill the Pure Forms first; they will cause more problems then the shielded Combat Forms. As you will not be seen, try to "assassinate" as many Flood as you can, especially Pures and Elites. Run forward to the Sanctum. In the center there will be some sort of podium: Cortana's stasis field. Go to the stasis field and bash on it until it breaks to free Cortana and start a cutscene.

If you want to clear it, there are some incindary grenades, cloaking, Brute Shots, some other weapons, and near the place to the Sanctum is a Covenant Weapon Case with 2 fully charged Energy Swords.

Part 2: Nor Hell a FuryEdit

The Reactor Room, Again Edit

Now you've got Cortana, it's time to get out. Cortana will tell you to destroy the reactors to destroy the infested city. As soon as you return to the reactor room, you will be greeted with both Combat and Pure Forms. Take out all attacking hostiles in the room before opening up the reactors. There are plenty of Stalker Forms in the room; however, they can be ignored as they don't react to the player (don't confuse these for active Stalkers). Open up the reactor cores and destroy them. You can destroy it from a distance with the Brute Shot, or jump onto the exposed core and bash it. If you jump to the reactor core, jump back once you finish or you will drop to your death.

Once all three reactor cores are destroyed, a new area will open up. Be wary that a Combat Form is lurking behind the door, and safely take it out before proceeding.

Drop down into the long hallway before the spiral. Combat Forms are running away, although they will try to kill you after running a while. If you have your Cloaking, use it and run past them as there are also Carriers that can kill you on higher difficulties. Run back to the Terminal Room.

The Terminal Room Edit

There are no enemies in here, unless you're playing on Heroic/Legendary, when another group of Flood meets you. If you still have your Cloaking (from the spiral or reactor room), use it and rush past the enemies. When you near the area you dropped down from, a Tank Form will bash the door and send some containers flying; avoid the containers as the high speed can kill you. Run into the wired area; any Flood in the terminal room will not pursue you once you enter

Going BackEdit

When you go back to where you got your first Gravity Hammer, there is a Combat Form running from the area. If you are playing on Heroic/Legendary, a few extra Combat Forms might appear, including one with an Energy Sword; take it out. You will later run into a few Carrier Forms, which you can dodge. Keep making your way back to the first large room.

The Pelican Edit

After you make your way through this area you'll run into the first large room again. You'll find the Arbiter (solo only) who will be cleaning out the Flood. The only Flood there are Carrier and Pure Forms. If you left the Flamethrower when you first reached the Pelican, the Arbiter will be using it. Run past him and straight to the Pelican. Hop on board and...

What you weapons have at the end of this mission will be at the last and final mission as your starting weapons. However, you will lose your support equipment.

Speed Run WalkthroughEdit

If you're having difficulties beating this level the traditional way, you can attempt to adopt a speed run strategy. On Legendary, this method is suicide and you won't advance much beyond the Pelican, but on lower difficulties you can make it through nearly every area without a prolonged engagement with the Flood.

Part 1: RampantEdit

When the level starts, you will drop in with an Assault Rifle and a Shotgun. These will be useful for a short while, but you'll need to switch to other weapons sooner rather than later. Progress through the Infection Forms running, don't waste your ammunition 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. You should soon get to the point were you drop through the hole in the floor.

When you drop through the first porta you will be assaulted by several Combat Forms. You need to fight these. There is one Combat Form with an Energy Sword, which will definitely come into use a bit later on in the level. When the Carrier Forms attack you, throw an Incendiary grenade to prevent Infection Forms from spawning.

The next room is going to be your fastest skip of the level. There are a few things to note though. To the left side is the opening with the Pelican. There is a Flamethrower and some weapons and ammunition out there, but unless you're already really low on ammo, don't go near it. You should run straight forward, using your Assault Rifle to clear a path to the porta. Once the porta closes the Flood won't follow you.

In the next area there will be several regenerating Combat Forms. Use a grenade and your Energy Sword to make short work of them, then swap your Energy Sword for the Brute Shot (which provides strong melee plus heavy projectile damage). Your weapons should now be an Assault Rifle with about 1/4 of the ammo left and a Brute Shot.

Drop through the hole in the floor. There are loads of Flood here, mostly Stalker Forms that will change into Ranged and Tank Forms, that will all be trying to take you down. Run forward with your Brute Shot out, shooting Ranged forms and meleeing the Tank Forms. Once you reach the center of the room you should get a Cloaking device. Don't activate it yet. Run straight forward out of this room, into the next area. Once you see the Carrier Forms, stick them with grenades. Advance. When you reach the left turn bring up your Assault Rifle and activate your Cloaking. You should be able to make it to the end of the hall without needing to engage, but if your Cloaking fails, the Assault Rifle will make short work of the Combat Forms.

When you go through the porta into the next area, swap your Assault Rifle for a Carbine in the weapons case. Keep the Brute Shot, even if it's out of ammo its melee is worth keeping it for now until you can get more ammo.

Kill the Combat Forms you can see, and melee any Stalker Forms that get close to you. Then run. The path on the far side of the room runs up and counterclockwise. If you have ammo left for your Brute Shot, you are much better off, because you can melee any Combat Form that gets close and a single grenade will kill a Ranged Form with an accurate hit. Grab a Cloaking but don't activate it yet. Just keep running and gunning with the Brute Shot, as it is most effective in this room. There will be a Brute Shot reload at the top of the room just before the porta.

The reactor room is your last challenge here, but just activate your Cloaking at the end of the long empty corridor before the reactor room and run straight forward to the center of the room. Turn right and run to the wall, then turn left and run to the door. You should be able to accomplish this without becoming visible again. Head through the door and down the hallway. Bash the stasis field to free Cortana.

Part 2: Nor Hell a Fury Edit

After the cutscene, head back the way you came. In the reactor room you have no choice but to fight the Flood. Use your Energy Sword to clear out the room. You'll have to be quick, as there are a number of foes here and if you aren't swift you'll be sent back to your checkpoint. Once you've cleared your balcony, swap your Energy sword for a Carbine and snipe any Combat Forms across the room. Then swap the Carbine for a Brute Spiker and finish off any Ranged Forms that remain. Load up your Brute Shot, and grab a Carbine. Use the Brute Shot to blow up the reactors, and run. Fall through the hole in the floor and run down the narrow hallway from earlier using your Carbine and grenades to take out the Flood.

Once you return to the terminal room bring up your Brute Shot and run forward. Toss Frags and use your Brute Shot to clear the area in front of you, and only in front of you. Keep moving forward and don't look back. The Flood will not follow you from one room to another, so move quickly and you won't need to fight as much.

Eventually you will reach the room where the Pelican is found. You will find that the Arbiter has joined you, with a Flamethrower. Just let him do the killing, and run past all of the Flood to the Pelican. Go into the Pelican and escape.

Notes for Legendary PlayEdit

Tips & TricksEdit

  • Know how to use every weapon to its greatest effect.
There really isn't any weapon that is weak in all situations. The only exception is a Plasma Pistol overcharge—while it takes out shields 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. 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, although this is helpful when you use the Iron Skull in this level. Try using anti-Flood weapons, such as the Energy Sword, Plasma Rifles, or Brute Shots as these are plentiful in this mission.
  • Know how to use grenades.
Get the most out of your grenades, use them on clusters of flood, 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. Never stick grenades on Combat Forms or blindly throw them as this can waste the grenade and burst multiple growth pods.
  • 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. Cloaking is good for speedruns, it is also effective for crossing the larger open spaces without detection.
  • Pay attention to your surroundings.
It sounds ridiculously obvious, but more so than any other level it is true here. The Flood blend with the background and often times your radar will not detect the enemy because they are stationary. Always check behind you and be methodical when clearing areas.
  • Know your Flood.
Each variety of Flood has a specific weakness. No one weapon will be effective against all (for example; The Energy Sword is excellent against shielded Combat Forms and Tank Forms, but its range makes it unsuitable against Ranged Forms). Understand that your best chance of survival is knowing what combination of weapons will provide you with quick short range attacks and excellent range, to maximize your overall damage.


Activating Skulls on this level is at your own peril, but here is a breakdown of skull use on this level and how it will affect your gameplay.


  • Iron
Due to the difficulty of this level, using Iron is not recommended. If you do use it, be utterly methodical in clearing areas. Leave nothing intact, and be very precise in your accuracy.
  • Black Eye
There are no Regenerators and many situations where you can die very quickly. Not recommended due to the difficulty of meleeing the Flood.
  • Tough Luck
The Flood often don't have anywhere to dodge to, and they usually forget to dodge anyway.
  • Catch
Activate this skull if you have it; the Flood don't use grenades, but they will drop more when they die (espically Ranged Forms), and will cause many deadly chain reactions if you throw a grenade near one, the only detraction here is large chain reactions can also burst growth pods. Flood also tend to avoid grenade attacks, so this is usually not recommended unless they are decently scattered around.
  • Fog
You will be surrounded very easily. However as your radar can often be deceptive on this level, if you do use it you're really not losing all that much of an advantage. Just listen to the screeches of the Flood to indicate if they are close or far from you.
  • Famine
Ammunition is scarce on this level, therefore this skull is highly discouraged. However, there are multiple ammo lockers with full ammo, and several weapons are quite common, such as Brute Spikers and Plasma Rifles. Using these weapons often with a decent amount of meleeing will make you suceed.
  • Thunderstorm
You will simply get more Elite Combat Forms with this skull active; however, they appear throughout the whole level anyways, so the only issue is having to deal with their shields on higher difficulties. It does mean more points if this skull is used, because Elite Combat Forms give more points then their other Combat counterparts, which is pointful for gaining the main achievement here, but if you struggle to take down the Elites, avoid turning this skull on.
  • Tilt
This skull is probably the most annoying, but also the easiest to get around. Your plasma weapons will become very ineffective, but projectile weapons like the Spiker and Human weapons are twice as deadly. Being able to aim properly is key here as headshots with the Carbine aren't affected.
  • Mythic
Much like the "Tilt" skull, for experienced players it's going to be more annoying than anything else. Accurate fire and knowing your weapons will effectively negate the consequences of activating this Skull. For inexperienced players, and those with difficulty aiming, this skull can be a death sentence.


  • Blind

No HUD, you cannot see ammo, grenades crosshairs or guns. Not suggested because the majority of Flood will be Brutes, and you will have a hard time headshotting them. Poor shooters can also hit growth pods which can be very deadly if multiple are shot at.

  • Cowbell

Bigger explosions. Stay away from grenades you toss, carrier forms, and any other explosions. Useful to get rid of tightly grouped pockets of Combat Forms with a Carrier Form around. However, explosions can cause growth pods to burst open.


No effect on this level. Use anyway for more points.

  • Grunt Birthday Party

No grunts on this level. Useless.

Depending on what you use and how good you are, Thunderstorm, Tough Luck, and Grunt Birthday Party/Mystic, you will get enough points to get the achievement depending on how you use it. Examples are sticking foes, assasinating them, using a Needler, headshots, etc.


  • This is the largest level in Halo 3.
  • This level has 2 skulls, though one is rendered useless (if you got it before).
  • This is the only level to give a lot of Incindary grenades out (there's one at the start room).
  • This level has an opposite toll. Instead of getting Human Combat Forms and Brute Combat Forms often, it is Elite and Brute Combat Forms that come.
  • This is the only level where your only headshot comes from Carbine.
  • The terminal on this level does not show anything but a Cortana moment.

Not Legendary NotesEdit

  • There is no difference in how you should approach this mission whether it's on Easy or Legendary. The only difference is in the overall numbers of Flood (on Legendary they can seem unending) and in how difficult it is to kill them (headshots, not withstanding) If you can beat this mission on Normal without getting killed, it's a fair bet that you should be able to complete it on Legendary. Remember to take it slow, no battle has respawning flood.


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The Covenant
Halo 3 Campaign Walkthrough for:
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