From Halopedia, the Halo wiki
This is a walkthrough for the Halo 4 campaign level Midnight. It is written for play at the Legendary difficulty, but contains notes for lower difficulties. It is important to note that as this walkthrough at the Legendary difficulty, all strengths of enemies reflected are at the Legendary level.
One Last Shot (Rally Point Alpha)
Blow this Thing and Go Home
This section is quite repetitive, so here are a few tips for getting past the trench:
Once you have made it past the "trench run", you will be deposited in the first real combat section. The large, bowl-like area you will find yourself in is the top of the Didact's ship, and your job is to get inside it. To do so, you must destroy the four anti-ship cannons around the ring of the bowl. Their power cores will be marked with way points; simply pick one to start with as a target and fly in a slow circle around the bowl. Along the way, destory any point defense guns that you can. Each one you take out reduces the amount of fire you have to dodge, meaning that you can destory the main power cores easier. The moment the last one is eliminated, a cutscene starts, ending the vehicle segment.
... To the Grave (Rally Point Bravo)
Force Can At Least Be a Delay
You go on foot with a Battle Rifle and SAW, as well as a Hologram equipped. Walk through the doors on the left and destroy the three Watchers that appear in this room with the BR before they can spawn Beam Turrets. Go to the left to find the fourth Watcher, then destroy it. Take note of the "Nuclear Device Acquired" text on your HUD, as the Master Chief has already attached the HAVOK nuclear warhead onto his back.
At this point, your BR should be almost dry on ammo, and there's no use for it beyond this point, so swap it out for a LightRifle before entering the next room and later sections of the level. The LightRifle is an invaluable tool for this mission, so make sure to always have one equipped. It is also highly recommended to fire with the weapon scoped in.
The next room has two Knights, a standard one and a Battlewagon. This Battlewagon is always programmed to deploy his Watcher from a spot directly in front of where he spawns. Right as he deploys the Watcher, shower him with SAW bullets and Frag Grenades. However, if he didn't die, he will teleport away. The Watcher he deployed can be a serious problem, so destroy it immediately with the SAW. Once the Watcher is dead, eliminate the Battlewagon with the SAW and LightRifle, but be careful of his Scattershot, for he can instantly kill you from even a slight distance with it on Legendary. After killing the Battlewagon, pound away at his lesser LightRifle-armed comrade with the LightRifle until he falls. Before entering the next room, make sure to restock on LightRifle ammo and Pulse Grenades. You can also grab the Battlewagon's dropped Scattershot if you wish.
There are no Knights in the next room, only two Watchers who spawn in Crawlers. Kill the Watchers as quickly as possible in order to avoid having to fight the Crawlers. However, if the Crawlers do get spawned, kill them as well. At this point, it is highly recommended to use the Hologram to confuse the Prometheans to leave them open to your attacks. In the central structure of this room lies the seventh and last Terminal, so if you are planning on obtaining the "Terminus" achievement, do so now. Regardless, restock on LightRifle ammo before opening the next room.
There are two Knight Lancers armed with LightRifles and a Battlewagon. Activate the Hologram to confuse the Lancers and keep your distance from the Battlewagon as you take him down with a flurry of LightRifle rounds until he falls. Refill LightRifle ammo if needed and attack one of the Lancers. If he performs his zigzag charge attack, pull out a Scattershot and walk back so as to avoid dying to the Lancer's fatal charge. If he completes his zigzag charge but does not hit, shoot him with Scattershot rounds until he falls. Repeat this same process on the other Lancer. Alternatively, you can also blow up the nearby power core to deal extra damage to them, but make sure to not get too close.
Of Snipers and Incinerators
Once this room has been cleared, refill your Scattershot and LightRifle, and then grab an Autosentry if you wish to do so, although it's not exactly necessary. In this last room, Cortana will say, "I recommend entering the doorway to your left." Open up the door on the left and fall down the shaft. Don't worry about dying from fall damage here, as the gravity lift will slow your descent down. Run down the hallway to enter the room with a large chasm and a platform at the end with an activation port. Plug Cortana into this activation port and enter the portal to your left.
You will be teleported into a hallway filled with Crawlers, including one Crawler Snipe. Headshot the Crawlers that appear with the LightRifle and make sure to watch out for the Crawler Snipe, for he can score an instant kill on you on Legendary. Alternatively, you can use the Autosentry to kill the Crawlers and save ammo, although this is more difficult given the Autosentry's lack of resilience against the Binary Rifle. Either way, once you kill the Crawler Snipe and all the other lesser Crawlers in this hallway, drop your Scattershot for the fallen Snipe's Binary Rifle and make sure that you still have sufficient LightRifle ammo before entering the next portal.
The portal teleports you to the same platform that you saw earlier when you inserted Cortana into the system. This platform is filled with four Knights, including a Battlewagon, a Binary Rifle-armed Lancer, and the deadly Commander. If you didn't already fight Knight Commanders in the mission Shutdown, this mission will act as your introduction to these Knights. They are the highest-ranking Knights and are usually armed with the Incineration Cannon, which is an extremely powerful and deadly projectile launcher that can instantly kill you on any difficulty except Easy.
The Battlewagon, Lancer, and Commander deploy Watchers almost immediately after you spot them. Take them out with the Binary Rifle, and this should leave you with 3 (1 + 2) rounds left on it. Save the Binary Rifle for the Lancer. First, take out the Suppressor-armed Knight with the LightRifle and then refill your LightRifle. Immediately to the right of where the portal teleported you to is a weapons cache with two LightRifles (worth 216 total rounds or 72 shots) and two Pulse Grenades.
When engaging the Lancer, stay in cover and headshot him twice with the Binary Rifle to kill him. If you did not land a killing blow on him with your second Binary Rifle shot, quickly switch to the LightRifle and shoot the Lancer in the head; however, fighting him with a LightRifle is not a wise idea due to his deadly attacks. Should you actually kill the Lancer, grab the Binary Rifle he dropped and use it to destroy the Commander by headshotting him, but watch out for his Incineration Cannon. If you think he is about to fire, immediately get to cover. Once the Commander is dead, grab his Incineration Cannon and then enter the portal to the armory.
Den of the Crawlers
In the armory, you will find various weapons, including Battle Rifles, Covenant Carbines, Plasma Grenades, and a Gravity Hammer. Take the Hammer now if you wish to use it to obtain the "Chief, Smash!" achievement, but it's not necessary and that achievement should be done on lower difficulties. Grab a Carbine and leave the room with full Carbine and Incineration Cannon ammo (90 Carbine rounds + 6 Incineration Cannon shots). Plasma Grenades are optional, but helpful.
The exit portal in the armory leads you back to the same platform you fought all four Knight classes on. Immediately in front of you is a Knight looking away from you; assassinate him and swap your Carbine for a LightRifle. You will now be traversing through this platform in reverse, fighting Crawlers, Watchers, and Knights. However, this section is easier because the Lancers are now armed with LightRifles. Prioritize LightRifle shots on the Crawlers and Watchers, and save the Incineration Cannon for the Knights, especially the Commander that comes up at the end of this platform. The Watchers must be destroyed first so that they cannot revive any dead Knights.
After killing the Watchers and Crawlers, blast the Knights to oblivion with the Incineration Cannon. If you miss, just hope that the weapon's submunitions damage them, then finish them off with the LightRifle. You can even take out some Crawlers as well if they get too close to your Incineration Cannon shots. Use up your remaining Incineration Cannon rounds on the Knight Commander to finish him off. If you didn't miss too many of your shots, you should be left with one or two extra rounds. Once the platform has been cleared, swap out your LightRifle for your Carbine and refill your Incineration Cannon ammo before entering the next portal.
In this next room, there will be a huge horde of Crawlers later on. As soon as the Knight Lancer appears in the room, destroy him with the Incineration Cannon and headshot the few Crawlers here with the Carbine. Cortana will alert you of reinforcements. The Incineration Cannon here is not really needed, so drop it and get a LightRifle from the nearby weapons cache and use it to kill the Crawlers that appear. The Crawlers spawn in small groups of two or three from afar, making them prime targets for your ranged weapons.
Eventually, Cortana will summon two Beam Turrets that will fire at all Crawlers that come in to stop you. However, you are still better off relying on your LightRifle to kill the Crawlers, as the turrets act as distractions for the Crawlers at best. If you ever run out of LightRifle ammo, grab a Boltshot and use it, as it has headshot capabilities. After a certain amount of time, Cortana will appear for you to grab her. Grab her and escape through the bridge, with your Carbine and Incineration Cannon ready because the Crawlers will spawn endlessly to stop you.
Drop the Crawlers with Carbine headshots. If you see a large group of them, burn them with the Incineration Cannon. Try to avoid reloading your Carbine as much as possible here, as the Crawlers will use that as an opportunity to end you. Once you get close to the portal at the end of the hallway, the Crawlers will stop spawning.
Old Friends (Rally Point Charlie)
Arrival at the Composer
Walk into the gravity lift and take the conveyor lift at the end of the ramp. At this point, upon taking the conveyor lift, you will automatically fly to the platform ahead of you. Enter the hallway and stop at the armory. If you didn't grab an Autosentry, grab one now. Here, you will need to grab a LightRifle and a Binary Rifle. Grab these weapons and the Autosentry, and then exit the armory. Approach the end of the platform to bring up a terminal. Plug Cortana into it and watch as she screams and duplicates herself. The platform leads to two routes: Route A, on the left, leading to a tower full of Knights; and Route B, on the right, leading to a tower full of Crawlers, including a Crawler Snipe.
Route B is the safer option, so turn right and take the conveyor lift to the tower of the Crawlers. Engage the Crawlers with the LightRifle, making sure to score headshots as much as possible, and destroy the Watchers with the Binary Rifle, although you should save the Binary Rifle for the Knight Commander in this tower. Follow the ramps, eliminate all hostiles, and hit the switch to activate the light bridge. If you still need Binary Rifle ammo, grab from the Crawler Snipe.
At the top floor of this tower, there are even more Crawlers and Watchers here. Kill them all and a Knight Commander will spawn in at the end of the platform. If you still have ammo on your Binary Rifle, use all of it on the Commander and make sure to land headshots. Once he falls, grab his Incineration Cannon and then plug Cortana into the terminal. You should soon see the Composer's shielding begin to weaken. Refill your LightRifle and Incineration Cannon with ammo from the lower floor before flying to the next structure.
If this mission is played on Heroic or lower, the Knight Commander in this section will not spawn.
This structure has multiple Knights and many Crawlers, as well as Watchers that will summon Beam Turrets. Incinerate the Knights and take down the Crawlers, Beam Turrets, and Watchers with LightRifle rounds. Before you reach the Knight tower, refill your Incineration Cannon and LightRifle ammo. After all hostiles in this structure are down and you have restocked on ammunition, fly to the Knight tower.
The Knight tower is arguably the most difficult section in the entire mission, as there are a lot of Knights, including Battlewagons, Lancers, and Commanders. Right as soon as you land on the entry platform to the Knight tower, a Knight will spawn in. Incinerate him, and then destroy the Watchers and Crawlers in this area with the LightRifle. Follow the ramp, and you will find a Battlewagon and a normal Knight to your left. The Incineration Cannon is your best friend against the Knights here, so keep your distance from the Battlewagons and Lancers and use it on them. This is also a great time to use Plasma Grenades and Pulse Grenades; use them all up if you need to. Make sure not to miss any shots, though, and always make sure to restock on LightRifle ammo.
The Knight tower is virtually identical to the Crawler tower, so once you get to the top floor, you will need to activate a switch to make a light bridge appear so you can get to the top platform in this tower. This part here is the most difficult part of the mission, as on Legendary difficulty, there are seven Knights on this platform. Incinerate the first one that charges at you on the light bridge and then take out the first Lancer with the LightRifle, making sure to avoid him and his zigzag charge attack. There are two Knights here; a standard one and another Lancer. Kill them from a distance and then destroy the next two Knights that spawn: a normal one and a Battlewagon, which should be dealt with using the Incineration Cannon. The last Knight in this area is a Commander; he spawns when you get close to where the terminal is. Once he spawns, destroy him with the Incineration Cannon, but watch out for his shots also. Once all the Knights are dead, restock on Incineration Cannon ammo and plug Cortana into the terminal.
After the cutscene ends, take the conveyor lift back to where you first arrived and four Knights will spawn, including a few Commanders. However, these Commanders are actually much easier to fight, as they only have LightRifles instead of Incineration Cannons. Regardless, destroy the Knights with the Incineration Cannon and any other weapon you still have and Cortana will create a gravity lift that will take you to the last light bridge.
Once the cutscene ends, you will begin the final part of the mission which behaves similarly to the climbing and Elite Storm quick-time events in the first mission. Climb up back to the light bridge with the left stick and plant a Pulse Grenade into the Didact's chest (default button: LT). He will break free from most of his constraints, but will eventually succumb to the Pulse Grenade and fall off the light bridge into the slipspace vortex below.
Immediately start crawling to the nuke and once prompted, press the melee button (default: RB) to detonate it and complete the mission.