Unnamed Skull
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Level: Armory
Difficulty: Legendary
Text Display on the Screen: " None "
What it does: This skull makes enemies more aware of your location, it seems.
How to Find the Skull: You'll see Sarge show up in an elevator at the beginning of the level. Wait there until he starts dissing on you and saying you need to get in the elevator. Now you have to wait for him to say "Would it help if I said please?" and then get in the elevator and go down. Get on the tram and look inside of the building. Press up against the doors toward the inside of the building, and then hold the X button and tha tshould give you the skull. It's on the green crates toward the end of the ride.