Iron is Halo 3's second skull and the second skull on the first level, Sierra 117. It is the game's first gold skull.

As a gold skull, it gives you and your cooperative play teammates the Iron achievement if any player picks it up during the game. After picking it up, it can be activated in the campaign settings page of the pre-game lobby.

When activated, this skull will force all cooperative players to reload the previous checkpoint if any of the players die, and will force a solo player to repeat the entire level if he or she dies.

Like its Halo 2 counterpart, when activated the Blind skull removes all interface elements from the screen. It is a silver skull, and provides no achievements or campaign scoring multipliers.

It is the first skull encountered in the game. It is out in the open, at the end of a rock outcropping overlooking the river to the far right of the pool where the Phantom drops off the first Grunt and Brute reinforcements during the first encounter of the first level, Sierra 117.