Skull activation

There is a complete skull guide with each ones location on this website. Here is the URL.

Http://www.supercheats.com/xbox360/guides/halo3/skulllocations.shtml

For what they do it tells you when you try to active them in the in the meta game menu.

In the campiagn lobby press X to bring up the skulls menu.

Or...

Gold Skulls

Iron- In co-op, if one player dies, you all restart at the last checkpoint. In individual games, if you die, the entire mission restarts.

Black Eye- The only way you can recharge your shields is by hitting/meleeing your opponents. (Press B to hit/melee).

Tough Luck- All of your enemies will be able to dodge your grenades, plasma pistol bolts, needles and vehicles better.

Catch- Enemies through more grenades, but drop more when they die.

Fog- Your radar disappears.

Famine- Weapons dropped by enemies will have less ammo in them than usual.

Thunderstorm- All enemies go up one rank. (They do more damage, have more health and have better weapons).

Tilt- Enemies have better resistance to your weapons. (Your weapons won't do as much damage to them).

Mythic- All enemies have double there usual health.

Silver Skulls

Blind- You lose your HUD. (You can't see your health, radar, ammo, grenades etc).

Cowbell- Explosions are bigger.

Grunt Birthday Party- When you shoot a Grunt in the head, they will explode into confetti, and you�ll hear children cheer, �Yay!� in excitement.

IWHBYD (I Would Have Been Your Daddy)- Unlocks hidden dialogue throughout the campaign.

N.B. When you go into the skulls menu, all of the skulls have a sort of riddle and don't actually tell you what they do.

Hope this helps!

Gamesmaster285

Look in the SC walkthrough section

Look in SuperCheats walkthroughs and guides.