Chapter 1: Clean Up
From the start, we need to work our way towards the structure with the anti-airguns firing away in front. As we reach the top of the hill, you’ll see a pair of rocky structures in the open area in front with a path between them. Hang out here for a moment as the covenant will come to attack you from either side of the rocky structures and the path down the middle. There is a good number of jackals and grunts backed up by an elite with a fuel rod gun.
Move up towards the rocky structures slightly to draw more enemies out. You’ll also want to note that there are two covenant turrets guarding the structure in front that will not hesitate to shoot you if you get in their sights. Continue to kill off any jackals, grunts and elites (2-3 more) in the lower area until no more come to get you.
Once you are able, continue up the path to the right of the structure, shooting any grunts on the top deck who mount the turret and any watchers you see flying around above them. Kill the elite and any other jackals or grunts before killing the guy on the turret at the top of the ramp at the far end of the area. Continue up the ramp when it’s clear.
Climb the ramp to the next level up, nothing that there is an elite sword carrier just at the top with a couple of grunts. You’ll want to maintain a position on the ramp here and use it as cover to move up and down as you deal with the threat at the far end of the platform - there is a Promethean laser turret and a couple of additional elites to take out. Once the elites are dead a group of 5-6 watchers will show up as well eliminate them and any other remaining bad guys.
Once the area is clear, a pair of objective markers will appear. We need to drop down and activate these but note that as you approach more watchers will show up and this time they will summon crawlers too. Deal with the Prometheans and once the second panel has been activated, you will need to fight your way back up to the top of the structure… Of course there are a bunch of new watchers and crawlers along the way.
Once you reach the top, approach the portal and it will vanish. A new objective marker will appear in the courtyard in front of the base. Return here and collect one or two of the power weapons on offer here and defend yourself.There will be around 4-5 knights, a bunch of crawlers and 3-4 watchers to deal with.
You will get a new objective to eliminate remaining Prometheans, and wouldn’t you know it that bloody structure is filled with knights, watchers and crawlers again. Simply mop them all up to have a pelican show up. Approach it to complete the mission.
Chapter 2: For Science
Once you are through the arch, continue up the structure to the right and when you reach the first open courtyard, head right again. There is a turret, two elites and a small group of jackals to eliminate here. After they are dead focus on destroying the four glowing green pillars.
Once you start wailing on these, additional covenant forces are going to rock up to try and stop you from getting at the rest of them. These include a jackal sniper or two and a large group of grunts. Once you have killed them, destroy the remaining pillars. Head back down the ramp to the courtyard. A covenant drop pod will appear and drop off several more grunts and an elite for you to deal with.
Afterwards continue towards the objective marker to the right. At the top of the slope kill the elite and the jackals before investigating the objective marker on the ground nearby.
This will trigger a group of 6-8 elites to spawn in the cave below and to the left of the platform we are on. 5-6 of these guys will come to hunt you down, whilst two of them remain below and pilot turrets in the cave. There are a couple of rocket launchers at the back of this area if you want to use them! Once the guys who came to you have been dealt with grab one of the sniper rifles nearby and snipe the remaining elites off the turrets below.
Once it is clear, head on down and through the cave and kill any remaining enemies. Activate the panel at the end to disable the blue shield. Continue through the now open archway. You will see a covenant drop pod deploy some more enemies in the area here (1 elite, a group of grunts and a few jackals). Kill them all and a second drop pod will spawn, dropping off 4-5 elites. Note that one of these is armed with a sword and another with a fuel rod gun. Make these two your priority!
Once the bad guys have been cleared out, continue around the right hand corner towards the objective marker and kill the group of grunts that approaches. As you round the first bend to the left, four elites will appear and attack. Wipe them out before proceeding around the next bend to the right.
As you do another drop pod will arrive and deposit another 5-6 elites on the pathway in front of us. Finally a phantom will appear to drop off one final wave of grunts, jackals and a lone, solitary elite for us to finish off. Once they are all dead or dying approach the shield to the left to complete the mission.
Chapter 3: Hacksaw
Note: There is a specific achievement 'Rescue Ranger' associated with this mission. To do this you must have at least one marine survive until the end of the mission whilst playing on Heroic difficulty or harder.
The goal of this mission is to assist marines in the nearby structures to repel a covenant assault. As you begin a couple of markers will appear on the screen. These indicate marines in trouble and you need to go and help each of them out.
As you arrive at the first set of marines, kill the jackals and grunts attacking them and make sure to take out the sniper jackals on the main structure up to the right. An elite will show up too and before long a drop pod will show up and drop off more grunts, elites and jackals for you to take down. Once you clear this bunch, the marines will join up with you to provide support.
Continue forwards to the next objective marker. These marines are under attack by a bunch of grunts (including one in a ghost), some jackals and a pair of hunters. Hijack the ghost if you can to make things a LOT easier. Once the area is clear, continue to the next objective and kill the grunts and jackals here. A couple of drop pods will deposit some elites in the area for you to clear out and some of the other covenant types as well.
After clearing all three marine squads, a phantom will show up on the opposite side of the central structure and it will drop off a wraith and several groups of jackals and grunts. Once this crowd has been eliminated radio chatter indicates another phantom.
As you arrive, a pair of phantoms will show up to attack you. Jump on the turret or grab a Spartan laser or rocket launcher from the ammo crates nearby and use them to destroy the phantoms. Fortunately they will not shoot at you which makes things a little easier, unfortunately though they will drop off around 4-5 elites on the ground below who will work their way to the top of the structure in a bid to kill you. Focus on killing the elites and once they are all dead, finish off the phantoms and a pelican will rock up. Head over to it to complete the mission.
Chapter 4: Pelican Down
As the mission begins, drop down the hill and continue up to the waypoint across the far side of the valley. As you approach a stream of grunts will also be approaching through the narrow dirt path from the other side. Kill them and proceed through, take out the jackal snipers up on the ledge in front and then any additional forces on the ground with you.
At the next objective marker, a drop pod will appear further up the hill in front and to the left and drop off some jackals in front. Continue along the path killing them and the 4-5 elites that also appear. At the top level continue over to the objective marker. As you approach a cloaked sword elite will appear from a crashed drop pod and attack.
Killing him will cause more enemies to enter your proximity from the nearby bridge so fight off the grunts and jackals here and when you reach the roadblock obstacles, take cover behind the rock to the left. Around the corner are 8-9 jackal snipers and a grunt on a turret overlooking the bridge, so to keep things safe we need to pop out and kill them individually and re-enter cover. You will get a sniper rifle drop nearby which will make things a lot easier.
Look further into the structural area. Once the gun has shut down, another pair of drop pods will land in this area. These house a cloaked sword elite and several standard elites and jackals. Kill them and work your way towards the next AA gun on the platform nearby. As you approach a phantom will fly in and drop off more covenant forces.
This group include more jackal snipers, some additional elites and a few grunts. Additional drop shops will continue to deposit elites and grunts on the higher levels, and they will come down to engage you as well. Deactivate the second AA turret when you can.
Proceed to the top of the structure and you will be greeted by a large group of grunts supplemented by a few elites and a pair of hunters. Once you have cleared most of these enemies, one final drop pod will appear and drop off a large group of elites. Simply wipe out the remaining enemy forces (marked with the red indicators) and head over to the objective marker to complete the mission.
Chapter 5: Gagarin
Remember this level from the previous chapter? We’re entering from exactly the same hallway as before, enter the big, empty room again.
Note: We can find another of those Red vs Blue Easter Eggs in this area! To find it, hug the left hand wall and enter the first overgrown tunnel you come across. When you reach the first fork in the road, stop and look up and to the left and you should be able to see a yellow box cheekily tucked away behind a fern. Shoot it to activate the egg.
Return to the main room and continue as before over to the far side of the area, through the tunnels at the back and up the ramp in the room. Interact with the indicated computer. Afterwards drop down to the floor below and activate the two switches on the pillars. Note that after activating the first switch, you will need to kill a knight and a few crawlers. Once both switches have been activated, a whole mess of crawlers and knights will spawn in the large room we walked through previously.
Head down the right hand hallway and kill all the crawlers in it and from the corridor eliminate any additional crawlers you can see in the room ahead. This will lure additional enemies to the end of the corridor including a number of watchers and knights. When it’s clear, continue out into the main room and climb the ramp to the right. Ignore the upper ramp from the moment and continue along the middle level until you reach the next objective marker. Interact with the computer here.
When it’s safe to do so, return to the back room we were in just before and interact with the new objective marker. Afterwards, kill the newly spawned crawlers nearby and return to the main room. Kill all the remaining enemy forces in here. There is a tonne of crawlers and a Knight Battlewagon or two scattered about the area.
Once the room is relatively clear, you’ll be given a new objective marker indicating the location of a computer on the opposite side of the room from the previous one. Activate this.
After the audio has played, we’ll need to work our way back up to the very center of the upper tier of the room and disable four power sources. There’s only one problem, more Prometheans have shown up. Fight your way through the knights and crawlers to the top platform. Eliminate any enemies hanging out up here and then press each of the four switches to deactivate them.
Afterwards you will need to destroy all of the enemies, after several waves follow the objective marker through the overgrown cave until you reach the clearing to complete the mission.