Halo 5 IRON SKULL Location
MISSION 3 / Glassed
The Iron skull requires you to play on Legendary difficulty.
Fight your way to the big battle area were you get the Scorpion tank. Hop in and drive up the hill. Directly after you make your second turn look left to see a Phaeton chasing an ally aircraft. Shoot the Phaeton down with your Scorpion. If you miss you can immediately try again by reloading.
After Shooting down the Phaeton, you will hear the Grunt birthday party sound effect. The skull has now spawned in 1 of 3 possible locations.
The first skull location is right behind you alongside the fence between two barrels.
The second possible location is on the roof of the building where you got the Scorpion earlier. It is behind a yellow barrel.
The third skull location is near the entrance under the little bridge like stone structure behind two boxes.