Once the tower is in sight there are two ghosts and don't destroy them because you will need them later. First spawn a killball in forge mode then spawn a few bubbleshields. Jump on top if it, then go up on the rocks to the top left. Alternately, take a Warthog, and park the front of it next to the cylinder. Then spawn a receiver node in the air wherever you like. Score over 15, points in the Campaign meta-game on the first mission. The Skull is located on top of the circular building next to the Anti-Air Tank.
You will need Xbox Live to perform this trick.
Halo: Reach Cheats
All enemies are given a field promotion, and ranked up to their next available level. It can hold small amount of ammunition but can fire in mid-reload. Walk over the Black Eye Skull to collect it. At the end of this path is some rubble, and in front is the Skull. Drive behind the Mongoose inside the Wraith, and use the boost. The Skull description reads "Pull pin.