Halo Infinite's Repository Skull is one of the most sought-after in the game. Why you ask? Because it provides the "Grunt Birthday Party Skull." Yes, the classic skull which causes Grunt's head to explode in confetti if you land a headshot. It's one of the few skulls that doesn't make your life a living hell.
The mission comes toward the end of the campaign, so if you're in the midst of playing, you probably didn't miss it. You'll be tasked to save the pilot and along the way, you can find the skull. You can watch the below video for a visual guide if needed.
As you progress in the mission, players will enter a wide-open area with two bridges. Unable to move forward without assistance, players will need to search around until they find a power seed. Go to the opposite door of the power seed by using your grapple and you'll find a spot to place the seed.
Cross the bridge until you come to the room with two large arches, Grapple up to the top and into a room, and you'll see a skull sitting there on the floor.