Off topic: Hey Jake havn't seen you for a bit.
On Topic: Heres how you get it.
Ok on Metropolis on any level get to the part where the banshees come you might want to kill all the marines because they might blow em up. Destroy everything except 1 banshee. Periodicly shoot the banshee so it follows you through the tunnel (best done with a ghost). When you get to the part where you go through the tunnel and where you see the jackel before you do that board it right as it goes through. It should say Loading and you'll be on it. After that fly to a the building on the right and you will see the Scarab gun (looks like a plasma rife) on 2 cones. What the Scarab Gun is... Infinite plasma rifle which can shoot the scarab beam.
Now known as Intoxication.