Take the Warthog, drive to the tunnels. On legendary, make sure you take both Marines for damage absorption. You may have to drive to the far left to avoid the Wraith gunner.
This level is easy until the tunnel section, which requires precise driving. Take the route shown. You shouldn't need to powerslide. Turn left and whip right to get onto the ledge.
In the next area, turn via powersliding (LT). Continue powersliding for the turns beyond the Wraith.
The door will not open until the Wraiths and Phantom are dead. Use the board-nade glitch to kill the left-most Wraith easily. (Board the wraith and throw a grenade at the exact same time. This puts the grenade inside of the wraith and kills the driver almost instantly.) Then use the wraith to kill the other wraith and the phantom that drops off enemies. If you do not kill the left Wraith first, another Wraith will spawn.
Getting shotgun+rocket from the Marines on the stairs makes it easy to clear the Scarab later.
You may want to park and snipe the Sniper Jackals, then sword-fly to the Wraiths. You can carry over a Sniper Rifle from Outskirts for this purpose. You can board-nade the Wraiths, but keep in mind stickies are useful to kill the Scarab pilots faster.
Grab a plasma rifle and get a BR for a ghetto noob combo to clear the Scarab. The Ghost drivers on the Phantom will drop plasma rifles on the ground when they die. Cpl. Perez also has a plasma rifle.
Getting on the Scarab early only saves about 10 seconds, so if you mess it up, just continue through the level as intended.
Method 1: Grenade JumpEdit
You need 2 frags for this trick. Refer to the video for the setup. Text instructions:
Jump onto the lightpost and then grenade-jump onto the tall metal post. (It's wobbly, so if you mess up, you'll probably knock it over.) Align yourself with the edge of the far wall. When Sgt. Banks pauses between "I don't think it's stopping" and "Keep your head down," throw a grenade, and run+jump forwards. You should bounce off the Scarab's "eye" and onto the roof.
Method 2: SuperbouncingEdit
<instructions go here>
NOTE: If you go through this level too quickly, you can deload the Scarab. Monopoli does it all the time. There's nothing you can do but reset.
Once you get on the Scarab, the enemies will spawn after a set time, but you must manually trigger the pilots to spawn. The trigger to spawn the Scarab pilots is at the bottom of the ramp. There will be 3 in total, one of which is white.
Wait at the bottom of the ramp for the enemies to spawn, then run forward and shotgun the pilots.
A relatively safe way to kill the Scarab pilots is to noob combo them through a wall. After boarding the Scarab early, wait below for the enemies to spawn. Quickly run back to the front of the Scarab, and drop down, just to the side of its "eye". If you push against the wall, you should be able to see the pilots and kill them through the wall. Sometimes an Elite may seek cover behind a wall, so you might have to flush him out with your remaining grenades.