This guide shows the location of all the collectibles (1xSkull) in The Command Spire mission in the Halo Infinite campaign. If you miss a collectible and complete the mission, then you won’t be able to get the collectible without restarting the campaign.
Also Read: Halo Infinite Collectibles Guide
During the mission, you will come to a room with giant orange portal-like shapes with hexagonal beams going through them as shown in the picture below.
On both sides of the orange portal type shapes, you will find a passage. Go through the passage till the end of the hall.
Here you will see the Hexagonal beam coming out from the final orange portal-like shape and turn the right side. Grapple to the top of the hexagonal beam.
Then turn around and look for a ledge where you can grapple to reach the upper level as shown below. You might need a few tries before you are able to grapple up.
The upper level is quite dark. You can switch on the flashlight to see clearly. Look up to see another ledge. Grapple on the ledge to reach the upper level.
Then go through the doors to reach the mythic skull. Mythic Skull increases the health of the enemies.