Number of collectibles: 1
Head to the other servicing tower. On your way there, you will be able to switch weapons to those used by the robots. It is worth it to grab the Overkill, and after a while a nest will appear in your way, along with one heavier enemy with a Mulcher. You should wait for him to approach you, and then fire at him with the Overkill.
After you climb several ladders, you will go out onto the yard, which is again swarming with enemies. You can find the Buzzkill on this arena, and it can prove very useful at dispatching your foes. After the combat is over, you can find a collectible here. Enter the guardhouse and in the corner to the right you should find orders to collect.
In the guardhouse, on the upper floor you will find a lever, which opens the main gate. Pull it and keep moving. After you reach the next gateway, a boss fight awaits you.
You have to keep your distance, your foe is very slow, however, if you let him approach you, he will kill you with a single strike. Additionally, he is immune to attacks, until he opens up his ribcage. When that happens, you have to shoot at the exposed locations. When he is exposing himself, he also fires rockets, which deal a lot of damage but you can shoot them down in mid-air.
After the fight is over, the act will end.