Successfully complete Mission 1: Ghost Stories in Campaign mode on any difficulty to unlock Extinction mode at the main menu. Alternately, reach Level 5 in Multiplayer mode. In Extinction mode, four players fight aliens in a post-apocalyptic world.
To unlock the Ghillie suit in Multiplayer mode, select "Weapon Challenges" to see if the "Chrome Barrel Master" challenge is active. If it says "Challenge Inactive", go to "Operations", and spend one Squad Point to get new challenges. Repeat this process until the "Chrome Barrel Master" challenge is active. Then, complete the "Chrome Barrel Master" challenge to unlock the Ghillie suit.
Start Chapter 1: Point Of Contact in Extinction mode, and obtain the sniper rifle. Find the "Gil's Lodge Motel" neon sign in the first area of the game. Use the sniper rifle to shoot the letters "L", "O", and "L" (in order) in the word "Lodge" on that sign. If done correctly, the message "LOL" will appear in the center of the screen. Note: This may take a few attempts before it works correctly. Once the Easter Egg has been activated, for a short period of time, any alien shot will explode into golden stuffed alien dolls.
Search the indicated locations to find all 18 Rorke Files:
1. Mission 1: Ghost Stories: After completing the space section sequence, you will gain control of a character on earth. While running and dodging the falling ground, enter the first house on the right with a car in the driveway. Enter the front door to find the file on the floor.
2. Mission 2: Brave New World: After shooting down the two enemy helicopters, you will get on a vehicle and arrive at the HQ. Go to the the third floor to find the file on a table below the terminals on the wall (the door to the balcony will be on the right).
3. Mission 3: No Man's Land: Once you reach the area with the yellow crane after controlling your dog for the second time, continue forward until you enter a gray building to find the file on a desk, below the hanging monitor.
4. Mission 4: Struck Down: After breaching into the baseball locker room, immediately turn left to find the file.
5. Mission 5: Homecoming: At the beginning of the mission, after entering the first building and reaching stairs, turn left before going up to find the file on the desk in that room.
6. Mission 6: Legends Never Die: After getting past the flooded streets and entering a new interior through a wrecked walkway, kill the two enemies, then go to the desk where they were standing to find the file.
7. Mission 7: Federation Day: After cutting the window to make an entrance, go left as you enter the first hallway. Then, enter the first open doorway on the left to find an office with the file on a desk inside, in the back right corner.
8. Mission 8: Birds Of Prey: When you enter a room where Rorke is waiting later in the mission, quickly grab the file on the desk before the mission transitions into another part.
9. Mission 9: The Hunted: After the crash landing sequence, you will eventually meet up with your lost squad again. In the area you find them, follow the stream of water on the left up to a waterfall. The file is on a rock to the left of the stream, near the waterfall.
10. Mission 10: Clockwork: At the beginning of the area where you must use night-vision goggles and fight through the security checkpoint, look down the hallway to see the file through the window.
11. Mission 11: Atlas Falls: After entering a chamber where you are ordered to interact with the control room, before deactivating the regulators, look on the right to find a side room with the file inside.
12. Mission 12: Into The Deep: When the LSC is destroyed, you will have to escape sinking debris, and eventually reach a shipwreck. Immediately when you reach the enemy ambush, swim to the ocean floor to find file on a rock.
13. Mission 13: End Of The Line: Once you reach a silo and are ordered to take a picture, after going through the door with "Mantengase Alejado" on it, immediately go down the stairs on the left, and turn left at the bottom of the stairs to find the file.
14. Mission 14: Sin City: After going through the large mall and reaching the slot machines, an ally will lift up a shutter for you to crawl through. Then, turn left to find the file on a table next to the couches.
15. Mission 15: All Or Nothing: Immediately after the mission begins and you put on the ghost mask, turn around to find the file on one of the lower bunks, in the left row.
16. Mission 16: Severed Ties: After launching the rockets, an ally will lead you downstairs and open a door. After going through the doors, go down the hallway on the right, and enter the first door on the left to find the file on a terminal in the corner.
17. Mission 17: Loki: After there is an explosion and you float through a tube, you will enter an open area in space. The file is floating in mid-air to the right of the large bronze solar panel.
18. Mission 18: The Ghost Killer: When the mission begins, immediately turn around, and look to the right to find the file on a red tool chest, near your vehicle.