The "Pillar of Autumn" mission in Halo Campaign Evolved features several hidden collectibles, including four skulls that alter gameplay and one terminal offering additional lore. These can be challenging to find, especially given the mission's linear design. Earning the "Clean Sweep" achievement requires locating all of them.
Speed Limit Skull
This skull, which disables sprint, is located shortly after gaining control of Master Chief. Look to your right for a ledge marked with yellow warning tape. While a direct jump from nearby cylindrical containers is possible, it's difficult. A more reliable method involves jumping from the sealed cryo chamber units where Master Chief awakens, then leaping across the gap to the ledge. The skull is automatically collected when approaching its location at the far end of the ledge.
Magnified Skull
Following the objective marker to meet Captain Keyes will lead you to an armory labeled B02. Inside this room, amidst empty weapon racks, the "Magnified" skull can be found. It sits atop the third cluster of three weapon racks, easily accessible by jumping.
Perspective Skull
Immediately after meeting Captain Keyes, turn around and return to the bridge. Locate the two marines manning the helm of the Pillar of Autumn. Drop down behind them to find the "Perspective" skull, which changes the player camera to third-person, at the foot of the ladder.
Approach Terminal
Progress through the mission until you reach the room above where Master Chief was initially awakened, which is encountered after navigating a ventilation system. As you exit this room, take an immediate left turn into the adjacent room marked B04. The "Approach" terminal, which provides lore, is situated on the other side of this room.
