Halo 3 skulls

Skulls are easter eggs in Halo 3 designed to make the game more challenging or interesting.

Background
The skulls resemble those in the multiplayer game variant "Oddball", and can be used as weapons in much the same way but they lack information text to pick them up. They are usually hidden out of the way, so one must search for them, or else know where they are, to get them.

Do note that in order to obtain any of the skulls, you have to begin the level from the beginning and on Normal or higher difficulty. In most cases, you do not have to finish the level after first picking up the skull, so you can simply save and quit; nor do you need to carry the skull after picking it up. After you first pick the skull up, you merely need to press X at the level selection screen to select whether or not you want it, or any others, active.

"Gold Skulls" will grant you achievements when you first get them, but "Silver Skulls" will not. They are differentiated on the selection screen by their background, but are identical in-game. In the Campaign Scoring mode, activating gold skulls will grant you a multiplier to the points you receive, depending on the skull and/or skulls.

Iron
Level: Sierra 117

Directions: This skull is at the end of the level. You can find it after a part in which you cross a bridge packed with enemies. It is located on the roof of the building to the left of the building where Sergeant Johnson is being held captive (facing the entrance). You can get up by jumping onto the pipes. Go all the way to the end of the rooftop, and the skull will be there.

Icon: A skull marked with a hammer.

Effect: If you die while playing solo, you will restart at the beginning of the level (you cannot revert to the last checkpoint at any time). If any player dies while playing co-operative, you will reset to the last checkpoint.

Point Multiplier: 3x

Black Eye
Level: Crow's Nest

Directions: As soon as you start the level, move to the end of the first room where there is a locked door you will use later on in the level. The door is facing what appears to be empty weapon racks. Carfeully jump on top of them. Above the racks there is a set of brown pipes connected to one larger pipe that you must jump onto. After that, jump on the larger pipe. The skull should be at the end of the larger pipe.

Icon: A skull marked with a smaller skull with a bruise under one eye. Also, the skull’s left eye is marked with a bruise underneath it.

Effect: Your personal energy shields no longer recharge normally. To do this you must melee an enemy with any weapon other than the Energy Sword.

Point Multiplier: 1.5x

Tough Luck
Level: Tsavo Highway

Directions: There is a point in this level where there is a sheild that is blocking all vehicles from passing it. Disable the sheild and fend off the drones that follow. Then you are on Tsavo Highway. To your left there should be a distinguishable yellow ladder. Safely jump down on the other side of the ladder facing away from you. The support beam creates a slight bridge that goes into the cliff. At the end of this bridge there is a cliff to your left. On the cliff you should find the Tough Luck skull.

Icon: A skull marked with three clovers.

Effect: Enemies dodge grenades, needles, and vehicle assaults with a far greater success rate.

Point Multiplier: 1.5x

Catch
Level: The Storm

Directions: In the outdoor area with an AA Wraith, some Ghosts, and later a normal Wraith, there is a silo-like building to the end of the cliff. Get up onto it (using a vehicle and a grenade or an ally), and the skull will be there. Note that if the non-AA Wraith's driver is killed (whether or not the Wraith is destroyed), the skull will disappear. This skull can be seen from several locations, including the boathouse where the sniper rifle is located and the landing where the regular Wraith is located. If the skull disappears, go back to your last saved checkpoint.

Note: There is a glitch in some games where this skull will not appear, even if the other instructions have been followed. In such an event, you should complete the entire campaign on at least Normal difficulty. Also note that the skull itself is affected by physics, so if a Wraith’s plasma mortar hits the top of the silo, the skull may be lost.

Icon: A skull marked with a diamond.

Effect: All AI-controlled units, friendlies or foes, throw more grenades, where applicable. The Catch skull has no effect on Flood, as they don't throw grenades.

Point Multiplier: 1.5x

Fog
Level: Floodgate

Directions: At the beginning of the level, you will walk into the destroyed city of Voi. As soon as you enter the city, there is a large building to your right after the missle silo. Take out a weapon with a scope (preferrably a battle rifle) and wait for a marine to start yelling to look in the air. A single flood soldier should appear on top of the building, ready to jump across the structure. Kill the flood just before it jumps. Hopefully, the skull will fall off the building so you can pick it up. This should take several tries. If you miss the flood or the skull is stuck on the building, just restart at the last save.

Note: Look up and to the right just BEFORE entering the city continuing to walk into it. You will see them run to the top ledge of the building, but you have a VERY limited amount of time to shoot the Flood creature. But the first time, if you're unable to shoot them, you will at least have a good idea of where to be looking the second time, and just revert to saved.

Icon: A skull marked with a swirl of fog.

Effect: Your motion sensor is no longer visible.

Point Multiplier: 1.5x

Famine
Level: The Ark

Directions: Shortly before you reach the area where Johnson flies down and contacts Commander Miranda Keyes, you will notice a small fork, the other path leading to your future destination. Pass through here, and head to the end of the stretch with the platform overhead. At the end, turn right and you will see a boulder. Use it to climb onto the platform, and walk to the last of the supports going up. It has an opening over the slanting part of the platform, and the skull is in there. Use a grenade (plasma works better) or deployable cover to get up. If you prefer, you can come back to here after getting the Scorpion and then get the skull.

Icon: A skull marked with a smaller skull.

Effect: All weapons that are dropped by enemies or are scripted to spawn on the ground (e.g., near a downed Pelican or group of dead bodies) have halved or reduced ammunition or charge. However, weapons found in cases still have the regular amount of ammo.

Point Multiplier: 2x

Thunderstorm
Level: The Covenant

Directions: There is a part in the level where there are two hornets and you are expected to take one and get to the third tower to take it down. When you get in, start to fly to the third tower. On your way there is what looks exactly like the third tower (only without all the land and enemies on it). Fly over to it. There is a long part of the tower that extends out into the ocean. There is a very tall ramp that leads up to it. At the end of the extension you will find the Thunderstorm skull.

Icon: A skull marked with a lightning bolt.

Effect: All enemies are promoted to the next available rank.

Point Multiplier: 1.5x

Tilt
Level: Cortana

Directions: The skull is at the top of the large circular room where Cortana asks your name, and says it’s very nice to meet you (your screen and movement won’t change for this one). To the left of the room will be some small, somewhat fungal, growths on the walls. Using these, jump up onto a platform. There will be some more nearby, so use those to get to a large circular platform with the skull on it. The skull will not be there after you reach the next save point.

Icon: A skull marked with a smaller skull with a hole in its head.

Effect: Enemy resistances are greatly increased. Where a particular type of weapon normally does slightly reduced damage (e.g., projectiles against Brute armor, or plasma against Brute flesh), it is instead greatly reduced.

Point Multiplier: 2x

Mythic
Level: Halo

Directions: Hug the right wall from the very beginning of the level. Soon you will reach a cave with a dead end, and the skull is on the ground, among the rocks.

Icon: A skull marked with a circle with a smaller circle in it.

Effect: The health of all enemies doubles.

Point Multiplier: 2x

Blind
Level: Sierra 117

Directions: In the beginning of the level, you and your troops will come across a waterfall with a phantom dropping off troops. Kill all of the enemy troops to get the out of the way, and move to the right of the area. There is a rocky outcrop, and one of the larger rocks extends into the water. The blind skull is at the tip of the rock.

Icon: A skull marked with an eye with a crossed out pupil. Also, the skull’s eyes are shaded white.

Effect: Your HUD and weapon are no longer visible.

Grunt Birthday Party
Level: Crow's Nest

Directions: You will come to a part where you drop down into a tunnel, and as soon as you land, Cortana will send you a message. There will be drones in the corridor, that you have to kill. Go to the end of the tunnel and slowly approach the ledge. If you look down over the ledge BEFORE falling, you will see a small green platform with an arrow pointing in. Face back where you came in the corridor, and slowly back away until you drop off the edge. The second you start to drop, start moving forward. If done correctly, you should just barely "grab" the ledge and since you SHOULD already be moving forward, it will walk you into the tunnel with the skull. If it still doesn't make sense as far as where, you can look down through the end of the corridor at the floor you're standing on before you drop down, and you can vaguely see another room underneath the grating under your feet. At the end of the hallway you drop into, there should be the Grunt's Birthday Party skull.

Note: If walking backwards off the edge does not work for you, take a gravity lift and use it to propel yourself back up to the room underneath the grating after you have jumped down off the edge.

Icon: A skull marked with a candle.

Effect: If a Grunt is shot in the head with sniper rifles, battle rifles, or pistols, confetti explodes out of it (the explosion causes minor damage to nearby enemies), and children cheering are heard in the background.

Cowbell
Level: The Ark Directions: After defeating the Scarab, grab a gravity lift from the small structure in the center, then continue on until you pass the room with a lot of explosive plasma containers. In the hallway after this room, there is a tall section with openings above the turning point of the hall, and the skull is in the top one of these. Use the gravity lift to get there (place the lift around the middle of the ramp). If your grav lift is destroyed, you can always revert to last save since the room containing the skull is a checkpoint.

Icon: A skull marked with a cowbell.

Effect: The force of explosions is increased.

IWHBYD
Level: The Covenant

Directions: After the Arbiter kills the Prophet of Truth, kill all of the Flood in the entire area between Truth's body and the elevator that you came up on. Jump through the rings in the following order: 4, 6, 5, 4, 5, 3, and 4, with "1" being the ring closest to the elevator and "7" being the ring closest to Truth's body. If done correctly, the rings should all flash in a chasing pattern, and the skull will appear on the small bridge leading to the platform with Truth's body. It takes about 5 seconds for the rings to flash.

Note: In some cases you may need to complete the level after getting the skull to unlock it, unlike with the others. This is not always the case, however. After getting the skull check in the level selection lobby whether it is unlocked or not. If not, reload your last checkpoint, get the skull again, and finish the level.

Icon: A skull marked with a double helix.

Effect: Unlocks new, often humorous, dialogue for the AI.

Trivia

 * "IWHBYD" stands for "I Would Have Been Your Daddy", after a Sergeant Johnson quote from Halo: Combat Evolved.
 * People originally thought that you needed to jump through almost two dozen rings to get the skull to spawn. Later however, people found out that only the last 7 rings are what mattered.