Floodgate is essentially a reversal of The Storm. Players will have to backtrack from the Covenant Anti-Aircraft Battery to Lakebed A, fighting their way through a massive Flood infection. The level is the first Flood-only level in the game, introducing Combat Forms, Infection Forms, and Pure Forms.


Finding your way around Floodgate shouldn't be much of a problem—you're backtracking your footsteps all the way to Lakebed A in the previous level. This is the first mission in which you fight the Flood, making it a new experience when fighting the newly evolved Pure Forms. Keep in mind the useful weapons when in combat with them and any other Flood, especially on higher difficulties. This is a good starter mission for engaging the Flood. You can test the best technique of dispatching them without dying, because although there are some instructions about where to go and what to do, there are a billion other techniques that work just as well.

The recommended skulls on Legendary are Tough Luck and Catch. Tough Luck may cost you a few multi-kill bonuses, but grenades aren't a vital part of your arsenal during this mission. Catch is, as in all other Flood-only missions, a consequence-free multiplier—the Flood don't use grenades, so leaving it inactivated is a waste. All other skulls except Famine are okay on this mission, so try activating one of them too. You may not want to activate Fog if you aren't skilled at close combat with the Flood. Due to its short length, this level is arguably the easiest level to beat with Iron activated. Mythic is a consequence-free multiplier, as there are no Covenant enemies present on this level. Tilt is not recommended on this or any other Flood level.

This is one of the Flood levels where you cannot get Plasma Grenades unless some of the Elites die.

Weapon instructions in this level can be freely followed, as you will receive new weapons upon completing the level—specifically, the MA5C Assault Rifle and a Sniper Rifle


New in FloodgateEdit

Introduced in this level...
New Enemies: Flood Infection Form, Flood Combat Form, Flood Carrier Form, Flood Stalker Form, Flood Ranged Form, Flood Tank Form
New Vehicles:
New Items:
New Weapons: Flamethrower, Energy Sword

Campaign ScoringEdit

Points information
Exterminator Achievement Milestone: 15,000 points
Recommended Multiplier: 8x (Tough Luck (1.5) + Catch (1.5) + Thunderstorm (3) + Mythic (2))
Time Bonus
0-10 min 3x
10-15 min 2.5x
15-20 min 2x
20-25 min 1.5x

Starting WeaponsEdit

Player V
Starting Point >
Mission Start Rally Point Alpha Mission Start
Rally Point Alpha
John-117 Primary Weapon
BR55 Heavy Barrel Service Rifle BR55HB SR Battle Rifle N/A N/A
Master Chief Secondary Weapon
MA5C Assault Rifle MA5C Assault Rifle N/A N/A
Master Chief Grenades
2 M9 High-Explosive Dual-Purpose Grenades 2 M9 High-Explosive Dual-Purpose Grenades N/A N/A
Master Chief Primary Weapon
BR55HB SR Battle Rifle BR55HB SR Battle Rifle BR55HB SR Battle Rifle BR55HB SR Battle Rifle
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 Grenades 2 M9 High-Explosive Dual-Purpose Grenades 2 M9 High-Explosive Dual-Purpose Grenades 2 M9 High-Explosive Dual-Purpose Grenades
Thel 'Vadam Primary Weapon
N'tho 'Sraom Primary Weapon
Usze 'Taham Primary Weapon
Type-51 Carbine Type-51 Carbine Type-51 Carbine Type-51 Carbine
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 grenades 2 Type-1 Antipersonnel grenades 2 Type-1 Antipersonnel grenades 2 Type-1 Antipersonnel grenades

Walkthrough (In-depth)Edit

It Followed Me Home (Mission Start)Edit

Storage AreaEdit

If you're skilled with the Battle Rifle and are trying to get the Exterminator achievement, you may want to look to the right of the path that is about to be described. There, in the distance, if you are quick enough, you may see several Flood Combat Forms assault a small group of Marines. They will begin to retreat, though if you fire at them, they may turn to face you, and strafe instead of running away. For quick kills without using a lot of ammo, aim for their chests to kill the Flood Infection Forms that reside inside of them. On Heroic you will get 38 points from that, and on Legendary you will get twice the amount on a headshot. When you're done with that, proceed as you normally would...

Backtrack down the path you took to get to the Anti-Aircraft Battery. Make your way down the hill, and enter the Storage Area where you previously fought the Brute Chieftain. There will be a building on your right. Just after the checkpoint—right when a Marine says, "All squads, report!"—a Flood Combat Form will appear on the roof and jump over the street. If you kill this Flood during his jump (or right as he starts to jump), he will drop the Fog skull. Collect Frag Grenades, and swap your Assault Rifle for the Gravity Hammer. Take the grenades from the dead Brutes and Marines in the area, and do not switch with any other weapon unless you're very bad with the Battle Rifle.

As you approach the Marines—some of which are gathered behind a pile of sandbags, standing next to weapons lockers—Combat Forms will drop down and start attacking your allies. You can use the Battle Rifle to knock the Combat Forms that fall down. You can throw a grenade, but if it kills to much of your fellow Marines you will get betrayed by the Arbiter (unless you play co-op modes). The Flood don't use weapons here, so smash them with your Gravity Hammer if they get too close. Otherwise, snipe them off with the Battle Rifle. On Heroic and Legendary, a squad of Combat Forms (four Brutes and three Humans), will approach from the blocked area and jump into the fray, so watch your back to avoid getting assassinated. After a while, all surviving Combat Forms will collapse and release an Infection Form that doesn't infect corpses. Stock up on Battle Rifle ammo from the weapons locker.


Inside this warehouse, engaging the Flood over open ground is clearly suicidal. Though only a few carry weapons, their sheer numbers will surely overrun you if you're not careful. Using the Battle Rifle, snipe as much Combat Forms as you can; the best sniping point is where the dead Brute is on the second room. If some Combat Forms get past, throw grenades or just wait for them to pop out and shoot them. After a while, a large squad of Combat Forms jump from across the room, and they use one-handed dual wieldable weapons. Shoot as many as you can, as after a while they collapse into Infection Forms that don't infect corpses. Backtrack to the weapon locker containing Battle Rifle ammo before proceeding.

There is some potentially useful equipment here, including a Trip Mine, a Bubble Shield, and a Regenerator; these items are common throughout the mission. The most useful is probably the Regenerator, as armed Combat Forms can rapidly deplete your shields.

The next wave of Flood is smaller. If a large group is headed for your position, shoot the Fusion coils as they pass by them; the explosion should engulf a few. Your biggest concern is to avoid being surrounded. The Flood will also come behind you, so watch your back. There will also be one Carrier Form, but it's too far to hurt you. Otherwise, this battle should be relatively easy. The metal walkway that leads to the next room is home to a Flamethrower. It's enjoyable to use, but relatively slow and limited in range—which can be problematic, as you'll really need to destroy Combat Forms quickly on Legendary. Use it to torch the prone Flood bodies, which is quicker than using melee attacks. Swap your equipment if you haven't yet for the Deployable Cover.

Clear off all the enemies and stock up on grenades if needed. Go through the given path and go down a hole, or break a window for faster access. When landing into this room a Cortana Moment occurs. Stock up on more Battle Rifle ammo, and if you haven't taken the Shotgun, you can swap your Gravity Hammer for them, although you should keep it until the next act. As you leave the room, a very large squad of armed Combat Forms appear (they use Spikers and SMGs). Use your Deployable Cover quickly. If done correctly they should go in one at a time, and you can throw a grenade onto your cover as the Flood will be too distracted trying to get through it rather than dodging it. Deal with the next squad, and go past the Suicidal Marine. There's a Regenerator near the Marine, and if you need to swap weapons you can for some dual-wielded SMGs.

Shadow of Intent (Rally Point Alpha)Edit

Lakebed BEdit

A friendly Phantom will deploy a squad of Elites at your location. They are a big help, but they can be a nuisance if you're actively seeking a high score—valuable kills will be stolen. The Elites also tend to jump into the line of fire when you least expect it, and their furious grenade lobbing could lead to you being unintentionally betrayed.

To increase their lifespan and your score, skip the cutscene and snipe the attacking Flood with your Battle Rifle as you approach. If you do not want the Elites to die too fast, use your battle rifle (if you have it), and start killing the Combat Forms by jumping and so forth. Once they reach the ramp, they will slowly move to your position (their walking speed), allowing for easy headshots and points for your Exterminator achievement if you haven't gotten it. Deal with the Flood quickly, as on the harder difficulties they will die almost instantly and leave you with no allies apart from the Arbiter. Since the Flood attack up close, the Elites will also attack them up close and rarely switch to their Energy Swords. They also have a very poor melee attack that barely does any damage on them, so try to kill as many as you can so they don't do this.

Most of the time, there will always be an Elite Combat Form around, but it's not strong to harm you and your allies a lot. This is only if you stay in the area too long without starting the cutscene. This Combat Form at the moment does not use shields, so snipe it if you want to as these give the most points out of all Combat Forms.

(Occasionally, the Catch skull may cause them to grenade themselves off the cliff and to their deaths.)

The Elite landing party will thin down the force of Combat Forms situated on the side of the lakebed. If you find any intact Flood bodies, destroy them to prevent their reanimation. When the area is visually clear, search for two Plasma Rifles to dual-wield and an Energy Sword. Approach the ramp slowly, and immediately pull back into cover as Combat Forms leap from the cliff to your left. Dispatch them at range using your Plasma Rifles/Battle Rifle. They usually carry Brute Shots and Shotguns at this point, so take care not to get hit, and be ready to duck behind cover.

More Combat Forms will advance down the ramp, so knock them over before they open fire. Two Carrier Forms will waddle down the slope; toss some Frag Grenades or Plasma Grenades to rapidly blow them up, and then aim to mop up the swarm of Infection Forms as they approach. Make sure no nearby corpses are reanimated, though the Elites and your default ally will probably have killed all of the Infection Forms.

If you were on the side, not going down the ramp, on the first elevator, on the other side, there is a full charged Energy Sword and 2 full charged Plasma Rifles. This is better because you do not have to possibly kill an Elite, and that NPC-held items will have a random charge amount. Also if you still have your Battle Rifle, there's a dead Marine that has 2 Frag grenades and a Battle rifle to expend all your Battle Rifle shots which can help greatly.

Factory BEdit

As you enter the factory, avoid trying to fight the Combat Forms in the open. The Combat Forms are in a very large swarm, using Spikers and Plasma Rifles (the former is much more common in this swarm). Snipe off as many as you can before proceeding from the low corridor, scanning the intact bodies for some dual-wielding action.

As you leave the low corridor, additional Combat Forms will drop down from the ceiling. They'll generally land in close proximity of each other, so drop your second Plasma Rifle and throw a grenade or two into their midst. Then, retrieve your second Plasma Rifle and dispatch any that remain. Quickly run underneath the walkway to avoid being shot by the second wave. They'll arrive through the door above, so stay alert. Wait at the bottom of the stairway to take out any that run down. The Arbiter will take care of the rest. It could help to deploy a Regenerator at the bottom of staircase.

If daring enough, you can lob grenades at the door to score several kills, or attempt to headshot the Combat forms coming out of the door. The Combat forms that come out from the door will either jump down or go down the stairs and attack there. Your Energy sword is perfect to knock them to bits.

If you used the Regenerator, there is another one beside a dead Marine and a loaded Battle Rifle with two more extra clips.

On the upper level of this building, you can find a second Flamethrower. This isn't the best of weapons to deal with the Combat Forms, but it should make easy work of the Pure Forms outside.

Lakebed AEdit

Another group of Elites is usually (but not always) dropped off as you exit the warehouse—they will be deployed if the previous group of Elites has been wiped out. This time, take advantage of their aid as you fight the initial wave of Combat Forms and the Pure Forms further ahead. Be warned that they will take little consideration when you run in front of them—it's easy to get caught in the crossfire and get killed by one of their Plasma Grenades. The Phantom that drops the Elites when you exit the warehouse will also help by shooting at the Combat and Pure Forms. Watch out for the Pure Stalker on the crates; the scenery and it's color makes it very hard to notice but it is on the pile of big crates. If you don't kill the Stalker on time, you'll have to deal with many Combat forms and a Pure Tank form and on Legendary will most likely kill off all the Elites that you had with you in Lakebed B or the ones that just joined you.

There will always be Elite Combat Forms, so be on the watch and use headshots on them to kill them fast before they kill you. These will be shielded unlike the ones you saw on Lakebed B, so be careful.

Make sure the immediate area is clear before picking up an Energy Sword to replace your Plasma Rifles. If you can't find one, pick one up the next battle. Detach the Machine Gun Turret and carefully walk along the concrete path. Use short bursts of turret fire to temporarily disable the Ranged Forms that attack from distance as you push forward. If you rush, there is a big chance of being surrounded, so slowly advance, dealing with any Combat Forms that draw near, and choose cover that shelters you from incoming projectiles. There are many Deployable Covers here, so make a valuable cover on your turret so the barbs on the Pure Range Forms will not hit you as much, as they are extremely accurate and can force you to leave the turret multiple times without them.

Proceeding slowly, the Pure Ranged Forms will turn into Stalkers or Tank Forms. Avoid being hit by the Tanks as they instantly kill you if they land a hit on you on Legendary. Use the Energy Sword to kill them quickly or mob them with Plasma weaponry. There might still be some Ranged forms around, so lob grenades at them to kill them quickly.

Infinite Devil MachineEdit

Finish your objective by heading into the Indulgence of Conviction and retrieving Cortana. Remember not to fire your weapon—if a stray bullet hits a Flood Growth Pod growing on the wall, it will release several Infection Forms, and since killing them does not earn you any points, there is no benefit in fighting them. However, you can knock some dead Elites down the hole and shoot the pods for more points if you are trying to get the "Exterminator" achievement. This is not recommended though as it is a waste of time and players low on ammo will not be able to kill the Infection forms. The Combat forms that you knocked down from the level above will not charge toward you unless you get too close to them, and you can easily score headshots on them. (they have no shields)

Walkthrough (Brief) Edit

It Followed Me Home... (Mission Start)Edit

Backtrack along the path you took to get to the Anti-Air Battery. On the left side, when first heading south, there is a Gravity Hammer lying behind an overturned vehicle. Swap your Assault Rifle for it.

As you enter the next section, where Marines are waiting for you, Combat Forms will drop from the roof. Take advantage of the Gravity Hammer's splash damage or your Battle Rifle's headshot capability to make short work of the Flood. After the engagement, you may swap your Hammer for a Shotgun if you so desire. Continue through the office behind the door through which you entered this area on The Storm.

Here, you will see a Marine being ambushed by Infection Forms. Your chance of saving his life is slim, though you will have to kill the Infection Forms regardless. Inside the main room, there is a swarm of Combat Forms. Get their attention by shooting or lobbing frags at them, and then pick them off with a Shotgun or Battle Rifle as they climb (or jump) up the stairs to the office. If you still have your Hammer and are feeling daring, you can exit the office, smash a few Combat Forms, and then retreat back to the office; staying outside, however, will get you surrounded and killed.

When the Flood have been dealt with, grab a Trip Mine, a Regenerator, or a Bubble Shield, and then continue forward. The next section after the wall of shipping containers contains additional Combat Forms; kill them. Go up the stairs, across the bridge, and around. Drop through the hole for a Cortana Moment. Pass the two weapons lockers, and then turn right. There are several Flood camping around the 180° turn; counter this by throwing two grenades, and then finish off any survivors. (Frags can be bounced off of the wall, to hit them without exposing yourself.) Pass the Suicidal Marine and continue.

Shadow of Intent (Rally Point Alpha)Edit

Several Elites will be dropped at your location. Aid them in killing the Flood, and then continue. Go through the indoor area. A swarm of Flood will jump down from where a swarm of Drones flew in The Storm. As always, you will be fine if you don't let them surround you.

When you get outside, kill the Stalker Form. If it turns its back and changes form, it can be assassinated. Kill the Combat Forms in this area, then deal with the Pure Forms. Grab the Machine Gun Turret, detach it, and walk down the path to the right, killing anything in your way. When you pass under the metal pipe, be careful because there are several Pure Forms. Kill them and make your way to the entrance to the Flood ship.

Alternatively, if you are skilled at deploying equipment in precise locations, you can place a Deployable Cover in front of the Machine Gun Turret (without detaching it) to create an instant machine-gun nest that is extremely powerful against Pure Forms. Like any machine-gun nest, it is weak against flanking; keep your Elites alive (give supporting machine gun fire) so that they can defend your flanks. If you are playing Co-op, your partners can defend you. One Ranged Form will be out of the machine gun's range, so kill it with your Battle Rifle. Make your way to the entrance to the Flood ship.

Infinite Devil MachineEdit

There are no enemies here and no risk of getting lost, so just charge through until you find Cortana. Don't shoot the Flood Growth Pods unless you want to make the journey harder for yourself. A swarm of Infection Forms can overwhelm you, especially on the higher difficulty.


Preceded by
The Storm
Halo 3 Campaign Walkthrough for:
Succeeded by
The Ark