This is one of the best levels in the game. It genuinely feels like you're breaking into a heavily fortified enemy base. Patrolling guards pepper the outside entryway, on the lookout for any would-be interlopers. Once you start the attack, they all start gunning for you. The closer you get to the mammoth-sized doorway, the more Vital Suits and troops try to stop you. Even after you're in you've got to deal with a blanket of security drones and even more troops ready to put a bullet in your back. It's a natural escalation of adversaries that makes sense and is relatively difficult without being absurd.
It's also one of the largest outdoor areas, meaning there are plenty of ways you can tackle this beast of a level. The general path is up to you, but we can pass along a few tips. Once again, aim for the legs of any VS that's giving you guff. Even a machine gun can take down the smaller Suits in no time. Also, a good starting point is to head west to the elevated platform right away. Grab the rifle, snipe the soldiers to the south (near the data post) and take out the Suits over there. From this point, you can either head back along the north side and work your way down the valley or stay on the current side and enter a VS of your own in a building next to the canyon. Either way, be sure you get the "T" mark behind said building and the rocket launcher underneath that first tall platform. As long as you aim for the feet, toss grenades frequently and avoid getting surrounded, you should be clear. Keep in mind that there are plenty of other Suits and troops coming - you don't want to waste a ton of rockets right away.
On the plus side, there are five disk grenades ripe for the taking near a broken-down semi truck to the north. Even better, just beyond this truck are two hangar doors. One houses another VS (the first of many along this path to the hideout entrance), the next is a fully loaded ammo depot. Anything you want, it's here. We recommend equipping a VS with a rocket launcher and Gatling gun for the battles ahead, but grenades work too.
If the rockets, disk grenades and VS aren't enough help, there's a grenade launcher on top of the jutting rock, also to the north. The single biggest mistake you can make is running too far ahead, alerting far too many enemies at once. Hang back, deal with what you can, ammo up and press on into the doorway (after nabbing the "O" token above the door, of course).
Despite the fact that you've spent the past 15 minutes assembling a small arsenal, you begin the next section of Level 7 with your regular armament. So, grab the rockets to the west, hit up the data post and move on into the very same wasteland you traversed in the third level. There's no worm, but there are several large Akrid roaming around, including a new, armored version of a bug you already know. Fly from one data post to the next with your fancy new VS, dispatching bugs when necessary. If you can avoid direct contact, do it that way. However, there are a lot of Akrid here, so be prepared for a seriously annoying bout of assaults. Amidst the chaos, be sure to grab the "A" token along the western ridge (near where you found "A" in mission three) and the "R" along the eastern wall.
Now for the out-of-the-way token that's gonna start a serious ruckus. Head north along the eastern wall, back to where you fought the VS at the end of the third level. You'll see the "N" mark resting on the ground in between bits of wreckage just past the data post. On your way back south (or at any point you get too close the exit out of this tundra) you'll catch the attention of two or three massive Akrid, a few enemy Suits and a handful of troops. Honestly, there's no reason to stand and fight. It's a giant gangbang of explosions and insectoid body parts, but it's one that you don't necessarily need to get involved in. Let them kill each other, head to the door atop the stairs and get out.
Alright, it's the home stretch. To the right you'll see a series of hallways running through a giant wall, guarded by a fleet of hovering, laser-guided drones. The moment you cross their path or send a stray bullet their way, they'll lock on and dog you to death. So, it's best you drop down two levels on the first platform, activate the data post and take out the first drone you see. Once it's gone, gun-butt the fence away and hop in the Gatling gun turret to dispense the rest of the drones from a distance. If they get too close, aim for their rotating discs - they're the only vulnerable spot on the drone when its protective doors are shut. Once you've cleared enough, get down to the bottom of that giant wall, leap off the edge leading into the drainage pool and look in the southwestern corner for the "D" token. You'll have to rappel down to collect it. Hurl some rockets at the missile defenses on the other side of the pond and you're all clear.
For the most part, the entire wall structure and its hallways are for decoration. You can certainly explore them, but aside from enemies and a few bits of ammo, there's nothing you need. Just get the "O" inside the small doorway at the end of the walkway and you're good to go. Blast through the closed northern door and proceed to the boss battle.
This should be a VS-VS battle, but if its electric powers and drone buddies prove too much, resort to tactical rocket strikes and expertly placed disk grenades (found just before the boss room, handily enough). The VS can transform into a drilling tank, but a simple hop-and-hover will avoid this rushing attack. Compared to the Green Eye, this boss is nothing. Do what you've been doing and it'll break apart easy.