Part 1: Any Landing You Can Walk Away From
After chief stands up, continue through the opening in front and through the door on the left of the room. Help the marines here by taking out the jackals at the end of the hallway before proceeding to the end of the passage and exit through a door to a hangar bay.
As you enter, a phantom will be dropping off a group of enemy combatants. We need to clear the immediate area. Kill the jackal sniper up on the raised platform to the right and then proceed to defeat the other grunts and jackals in the room. Enter the structure to the right. Kill the elite inside and pop out the other side to an open area
Below you'll see another elite with a few grunts. Instead of hitting these guys right away, try to take out the jackal snipers on the scaffolding across the way before eliminating the other forces on the ground. Continue across the area and into the door to beneath the next structure. Follow the passage here and enter the door.
As you do, it's fairly likely that another phantom has entered the area, so deal with its re-enforcements and head for the door to the left at the end of the docking bay once all of the baddies are dead. Kill the jackals inside the open door and then take out the group of enemies consisting of grunts, jackals and an elite or two at the far end of the room.
Try to take the guy on the turret and the snipers out first! When it's clear, head over to the now cleared part of the room and descend the ramp to the right. Kill any remaining enemies in the area before climbing up the next ramp and entering the door.
You'll be in a bright room with a set of stairs to the left. Kill the enemies here and climb the stairs to the very top. Clear the elite and the other enemies here and enter the door to the left. Inside you will find a pair of hunters we need to take down to access the next area.
Note: There is a specific achievement ‘Give Him the Stick’ tied into killing both hunters using only the sticky detonator. In the back right of the room is a small office area. Head in here and pick up the sticky detonator.
Give Him the Stick
Took out both Hunters using only the Sticky Detonator in mission 7
Once the hunters are dead, activate the switch at the back of the room for a story scene.
Part 2: The Composer
When you are back in control, head through the door to the right and exit into the large outdoor area.
Head across the rocky ground and enter the objective marker indicated structure; wait for the guard here to open the door for you and continue up the ramp behind it. Kill the jackal and grunt here and make your way towards the far door. As you approach it will lock, so backtrack to the door we entered from and look just to the left of it for a service tunnel. Enter this and follow it.
In the room at the end, kill any enemies in close proximity. You will also see a grunt on a turret down the passage to the left. Do not go down the tunnel or you will get slaughtered. Instead, look to the right for a room, follow the passage to the end and you will exit to the right of the turret allowing you to flank the turret and kill the rest of the grunts and the elite here.
You can enter the door at the end of the hallway to enter the next room at ground level or through the door to the left to enter the next room on a balcony. Clear out the room of hostiles. Note that along the right hand wall of the room are three emergency exits and each of these is going to open and release covenant forces into the room. These will release elites, grunts and jackals in various formations.
At the top of the ramp, turn right and enter the room. This one is almost identical to the previous room, with three doors on the right which will open. Eliminate the elites, grunts and jackals in the main room, and take out the jackal sniper on the platform at the top of the room. Once these enemies start dying the three emergency exits is going to open and release covenant forces into the room. As with the previous room, these will release elites, grunts and jackals in various formations. Once they are all dead, go through the door that opens on the second floor.
Follow the tunnel to the end. Enter the door here. You'll be on a circular balcony area. Just to the left, you will see a console. Look closely and you'll see a cloaked elite. Kill him and his other elite buddy hanging out in the left of the room. Activate the console. After a few moments, remove Cortana from the socket and head through the door on the opposite side of the platform from the entry.
Follow the hallway all the way to the end, killing the grunts and jackals as you go. Enter the door to the left at the end and climb the stairs. At the top of the stairs, clear all the enemies out of the hallway opposite the entry door - be careful though as one of the elites is packing an energy sword. Once everything is dead, continue through the door at the end of the hallway.
Part 3: All Things Lost and Found
You are in another semi-circular room. Look to the left for a Spartan laser if you feel like it and then continue over to the right side of the room to enter the door. Once you are outside, hop into the mantis. Now all we need to do is defend the area. A steady stream of phantoms (backed up with banshees) are going to pour in to the area to drop off enemies. We need to kill everything and whilst doing this you are going to have to deal with wraiths, ghosts, banshees and tonnes of infantry units. Luckily we have a mantis!
Once the enemies stop coming, return back across the rocky area to where we met the doctor previously. Enter the door. Go into the first door to the left and activate the control panel here. When you are able, hit the switch to the right of the door to end the mission.
Completed mission 7 on any difficulty