Chapter VI: Digging In
[Kill the Boomers.]
[Destroy the Reavers.]
This is pretty straightforward: KILL EVERYTHING THAT MOVES.
Head up to the turret to make quick work of the Locust in the graveyard below, but take cover if you're on the receiving end of too many hits. Focus on the enemies with the most explosive weapons, and try to save your big guns for the next wave. Eventually, your turret gun will bite the dust, so regroup with your squad and make use of your long-range guns.
Lancers and Hammerburst rifles are probably the best way to handle the incoming Reavers. Some Locust grubs will also try scaling the side of your rig, but a quick melee or chainsaw to the face will solve that little problem. Once you're clear to drill, a chainsaw-slash-bo-staff-wielding maniac will attack Dizzy and Tai — but you won't be able to help them.
Act II: Denizens
Chapter I: Scattered
[Regroup with Carmine.]
Soon after you get back on the line with Anya, you'll see Alpha 7 bust into the Hollow. Navigate the cavern and head towards the sound of gunfire. You'll be too late to do anything about the other Gears, but Carmine will be fighting for his life. Eliminate the Locust threat and head up to the damaged Grindlift and give the rookie a hand. Once you've regrouped with Carmine, Jack will try to reboot the damaged Grindlift.
If you're having trouble keeping yourself supplied with bullets, make sure to an ammo sweeps before heading up to the Grindlift. Give the incoming Locust a shower of gunfire in the meantime. Watch out for the Tickers, which will try to rush around your cover and blow up in your face.
[Help Omega Squad defeat the Locust attack.]
More Locust will hole up amidst a pile of Grindlifts, so use your cover wisely. Make sure to keep moving, since some of these grubs will be packing a Boomshot or two. More Tickers will be scurrying about, so try to melee them towards the enemy and blow them sky high. After the skirmish, you'll get another call from Anya, this time about some more of those weird earthquakes.
[Find the source of seismic activity.]
Chapter II: Indigenous Creatures
[Shoot the glowing fruit to lure the Rockworm.]
Head past the Rockworm on the left side path, but don't miss a hole in the wall covered by vines. You'll find a Grindlift, some ammo, and an addition for your War Journal next to the dead Gear. At the next Grindlift, you'll come to a fork in the road, so choose a path.
Rockworms will block off whichever path you don't choose, so pick a position and stick with it. Take care of the turret gunner first, and shoot down Locust as they descend the ladder. After that mess is cleaned up, do an ammo sweep and head up the stairs. There's another grub hole coming up, but you'll luckily be able to use the Rockworm for a covering position. In some cases, you'll need to shoot the ceiling fruit to move the Rockworm to a good spot.
[Break through the Locust defenses.]
At the next checkpoint, shoot down the Locust from their defensive post. The conveniently placed Rockworm will move down the path at a slow clip, so use it for cover until you can get a clear shot at the grubs. At the fork ahead, pick a route and get ready to do some sniper practice. You'll see a Locust patrol on the way; so if you're good on ammo, feel free to take a few shots at them. Feel free to laugh as Marcus counts his shots.
Locust will crowd the next checkpoint, so use the vehicles and nearby cover to make short work of them. Grab the turret gun when the Reaver pops up, and make it sorry it lived. Do a quick ammo sweep before the next crowd of Locust bursts though the large steel doors. They'll be packing heavy armor and Boomshots, so man a turret to efficiently mow them down.
Before leaving the area, there's a scroll in the rear of the defense post, so grab it and pocket it for your War Journal.
[Take out the Locust mortar squad.]
Alpha Two will come under fire as soon as their Grindlifts land, so rush the scene and help them out.
[Assist Alpha Squad.]
Sprint to the turret and take care of the Locust advancing on Alpha Two. Some Reavers will fly by, but they won't stick around to cause much trouble. If there are any mortar launchers lying around, use those at your own discretion.
[Search deeper in the cave network for the massive creature.]
Wow. That is one gigantic worm. Now that you've determined the source of the quakes, it's time to get moving again.