The "Heavy Burden" mission in Halo: Campaign Evolved, likely the game's final level, contains three skulls and one terminal. This bonus mission follows "Boarding Action" and "The Most Dangerous Game," tasking Master Chief and Sergeant Johnson with ending Harmony's project.

Eye Patch Skull

The Eye Patch skull disables all auto-aim for every weapon. To find it, progress through the mission until you reach a long bridge populated by grunts and jackals. Before crossing this bridge, look for a doorway on your left. This leads to a secondary bridge guarded by a pair of Elites. After defeating them, proceed to the end of this bridge, where the skull will be resting against the wall.

Harmonious Clarity Terminal

The Harmonious Clarity terminal is found after a cutscene on the bridge where star holo data is downloaded. Instead of following Sergeant Johnson up the slope, enter one of the two doors at the back of the room. Continue through the subsequent doors to find an armory where you can restock on weapons. Proceed through the final door, and the terminal will be located in the back-left corner of the next area. The player in Halo: Campaign Evolved looking at the two doors that lead towards the terminal.

Grunt Birthday Party Skull

The Grunt Birthday Party skull causes grunts to trigger celebratory explosions upon headshots. This skull is located in a three-story room with a prominent rock formation. After fighting your way through the ship, you will arrive at this room. The skull rests atop the rock formation. To reach it, drop to the floor below and stand on the brazier emitting purple flame. From there, sprint and jump. Upon landing on the rock, you can jump again to collect the skull in midair. The player in Halo: Campaign Evolved looking at the three-story room.

Efficient Skull

The Efficient skull grants more ammo drops when enemies are killed while the player is at full health. To find this skull, continue following the objective to regroup with Williams. You will eventually reach a moving platform. Remain on the platform, restore power to it, and get back on. After passing under the second bridge during this segment, you will enter an area with sections on both your left and right. Leap from the moving platform to the section on your left, then proceed to the back-right corner of this area. The skull is on the ground next to a locked door. The player in Halo: Campaign Evolved looking at the two platforms to jump on.