Skulls are used for basically modding or changing gameplay throughout the campaign, for example: The "Tilt" skull changes around damage and armor effectiveness for the enemy, or the "IWHBYD" skull, standing for "I Would Have Been Your Daddy", this skull changes around the covenant's speech to more rare, and usually funny dialouge. Also, collecting certain numbers of skulls will unlock unique achievments and armor pieces. You can check out more here:
http://halo.wikia.com/wiki/Halo_3_Skulls
Sorry there arn't any, The only skulls are in "Halo 3" Which are used in "Halo 3 O.D.S.T."
you can get all of the skulls on multiplayer. =)
They are skulls. idiot.
ok, go to youtube and type in "how to find all halo 3 skulls" then watch the video and get the skulls. yes, its that simple.
if you want to know where the skulls are all you have to do is go to youtube and put in "halo 3 odst mythic skulls" and it will show you how to get to them
find the skulls
There are no skulls in Halo Reach.
There is many silver skulls, look up a tutorial.
Find them your self
There are many Gold Skulls. Look up a tutorial.
http://www.halo3planet.com/halo-3-skull-locations/ is were I found them
By getting skulls.