As part of the Halo 3 Skulls easter egg, there are four Silver Skulls located throughout the game. The four Silver Skulls are the Blind Skull, Grunt Birthday Party Skull, the Cowbell Skull and the IWHBYD Skull.http://www.halo3planet.com/halo-3-skull-locations/ They are more difficult to find than the Halo 3 Gold Skulls.

The IWHBYD Silver Skull was the last remaining silver skull to be found, and was discovered by Halo3Planet.com.http://www.halo3planet.com/halo-3-skull-locations/iwhbyd-skull/

This page contains spoilers for the skull locations.

Halo 3 Level: Sierra 117

Difficulty: Normal, Heroic, Legendaryhttp://www.zimbio.com/Halo+3+Silver+Skulls

Effect: The Blind Skull disables the HUD of the player while it is on. No status can be seen for weapons, radar, motion tracker, shield or other attributes. First person arm also disappears.

Instructions: This skull is the first one available, and is located in Sierra 117, which is the first mission. To reach the skull, you must first have met up with the Gold Armor Brute and the enemy dropships should have appeared along the stream. There should be two of them. Head for the farthest dropship, following the stream until you get near the lake, then head to the right between the trees and towards the edge of the cliff. You will see a rock protruding over the lake a little bit. The skull will be on the rock. See video below for visual.http://www.youtube.com/watch?v=WlSWOB3MhIg

Halo 3 Level: Crow's Nest Difficulty: Normal, Heroic, Legendaryhttp://www.zimbio.com/Halo+3+Silver+Skulls

Effect: When killing an enemy grunt with a headshot, his explodes into confetti and children yell "Yea!" while Viva Pinata music plays.

Instructions: This is the second skull that can be accessed. When you are on your way to the barracks, just before meeting up with the Arbiter you will see an area of pipes with drones (look like insects) flying around. When you get to the pipe that will lead you to the Arbiter, stop before jumping and look down. You will see a small ledge with a green arrow pointing toward the wall under you. Jump onto the ledge by dropping off backward then moving forward immediately toward the wall of the pipe. This will land you on the ledge and allow you to see and access a secret room. The skull is on the floor in the middle of the room. See video below for visual.http://www.youtube.com/watch?v=WlSWOB3MhIg