Halo 2 skulls

A Skull in Halo 2 is an Easter Egg left in-game by Bungie to make the game more challenging or interesting, or to unlock potentials that would otherwise remain hidden. There is no information text to wield a Skull, as there is with a weapon, but it can be picked up just the same and its effect, ranging from making the game extremely difficult to letting one grenade jump higher than ever before, lasts until the XBox is restarted (Or in Halo 2 Vista until the game is restarted), but do nothing outside of campaign( with the exception of the Black Eye Skull). These Skulls are hidden very far out of the normal path of the level, sometimes even backwards.

Background
Every Skull except the Blind and Assassins Skulls are only available on Legendary difficulty (though on other difficulties the Assassins Skull will have no effect). The Blind Skull may be a very handy tool when recording video, and, fortunately, is very easy to activate.

There are some discussions saying that activating all Skulls will unlock a secret movie at the end like Halo: Combat Evolved, when you complete the last level on Legendary, or activate more plot revealing dialogue in the cut scenes. This has never been successfully tested. People curious about these unlocks, have found a fifteen-letter code on the Halo 2 Soundtrack and thought this code was a specific order these Skulls needed to be activated to unlock the secrets. This was proved false.

The Skulls are mostly used by players to customize their gaming experience by manipulating the game-play engines with the various Skull combinations. The most fearsome Halo 2 players will be playing with Skulls like a combination of Mythic, which increases enemy armor and shield strength greatly (Ultra Elites even require two overcharged Plasma Pistol bursts to compromise their shields) and Thunderstorm, changing all enemies to their highest rank; Envy, which allows the Master Chief to use Active Camouflage technology at the expense of his flashlight; and IWHBYD, which unlocks hidden dialog and causes the AI to interact verbally more often.

Note: These items are not actually part of the Halo universe, but are just tidbits that Bungie left in Halo 2.

Campaign Order

 * 1) The Heretic: N/A
 * 2) The Armory: Unnamed Skull
 * 3) Cairo Station: Thunderstorm
 * 4) ''Outskirts': Blind & I Would Have Been Your Daddy
 * 5) Metropolis: Catch
 * 6) The Arbiter: Grunt Birthday Party
 * 7) The Oracle: Famine
 * 8) Delta Halo: Envy
 * 9) Regret: Assassins
 * 10) Sacred Icon: Mythic
 * 11) Quarantine Zone: Sputnik
 * 12) Gravemind: Anger
 * 13) Uprising: Ghost
 * 14) High Charity: Iron
 * 15) The Great Journey: Black Eye

Anger
Level: Gravemind

Directions: After you save both groups of Marines, continue until you reach the first outdoor area with dirt and vegetation. Take a right as you enter this room and run up to the wall past the Gravity Lift that leads up to the sniper point. Get on top of the wall by going up the dirt mound on your left. Follow the wall and an invisible Gunner Grunt will spawn wielding a Fuel Rod Cannon. Kill him and reach the floating Skull called "Anger". Difficulty: Legendary

Effects: Enemies and allies fire their weapons faster and more frequently.

Status: Confirmed

Trivia: The Skull floats above a Gravity Lift ring. This Skull is treated as a "third" weapon rather than a pickup weapon. You can throw grenades (though there is no animation) and switch to primary and secondary weapons (though there is no side symbol, but a put-away animation).

Assassins
Level: Regret

Directions: Immediately after the gondola ride following the battle with the Hunters, there will be a building with two turrets on it. Enter the building and turn to your right. There will be a box, jump on it. From there jump to the adjacent light fixture, then to the ledge. The ledge leads to the area with the two turrets. Once there use a Grenade Jump to get onto the roof area, then, using Crouch Jumps and/or Grenade Jumps, follow the right side perimeter of the building. Once you have gone as far as you can go you will find a small grassy area with two Stealth Elites holding Energy Swords(one can be assassinated the other cannot) in their "angry stance" and the Assassins Skull between them.

Difficulty: Legendary

Effect: All enemies in game are permanently cloaked. Allies can sometimes see them but mostly they can't, so they can't help much.

Status: Confirmed

Note: This Skull also appears on any difficulty, and even on co-op play, but no Elites will be standing there, the flash and name will not appear, and the effect will not take place. If you kill a lot of Marines they will turn against you and become cloaked.

Black Eye
Level: The Great Journey

Directions: Eventually you have to escort Sergeant Johnson to Delta Halo's Control Room, who is in a Scarab. Follow him along until you see the Control Room in front of you. Directly above the door that Johnson blows open with the Scarab is an angled beam. Land your Banshee on this beam and walk to the top of the beam. Look down and to your left and you will see a circular angled wall. Jump onto this wall and walk to the top. Walk straight along the right-hand side of this area. You will have to jump over a small beam in front of you. Continue walking straight until you come to a grassy area. Keep walking up the grassy hill and go until you come to the point where can jump onto the angled support for the tower meets the grass. Jump onto the support and walk up the support. It's a very steep climb, so jumping while you're going up the support speeds up the walk some. At the first landing you will see the Black Eye skull sitting on a glowing white panel on the floor.

Difficulty: Legendary

Effect: Your shield does not charge normally. To charge your shields you must kill something (enemy, ally, or turret) with a melee attack (anything but the Energy Sword). You can charge your shields into the Overshield range by doing this (one kill will charge 100% of your normal shields). Also activates subtitles during cut scenes. Additionally, this skull causes the falling snow in the multiplayer level Lockout to disappear.

Status: Confirmed

Blind
Level: Outskirts

Directions:When you start the level, go through the door and kill the Grunt there. Right above the door you came through there is a light. Crouch Jump onto that and either Crouch Jump or Grenade Jump again (Crouch Jumping is easier), and you should be on the roof (or you can get the Sputnik Skull and only use one grenade). Look for a space between the two buildings, and go into it, at the end there should be four Fragmentation Grenades, a stand, and the Skull in front of them.

Effect: Your HUD becomes invisible. In other words, you cannot see your weapon (unless it's the Energy Sword, which has a glitched appearance with this Skull), body, shields, ammunition, motion tracker, or use your flashlight. However, well experienced players should be able to accurately judge where they are aiming with ease. Also, as enemies can still spot you, this Skull serves no tactical advantage whatsoever (although machinima makers will find a good use for this Skull), although hitting enemies with the Skull should kill them with only two or three hits. The effects of this Skull will last until you turn off the Xbox or eject the disc. Oddly, you can still see the shadow of your weapon, and even the Blind Skull itself. This skull appears in any difficulty.

Extra Information

An interesting possible message left by Bungie is seen in the form of the frags and scope. There are four frags, and the scope, which could be interpreted as "foresight". Also, since the Blind Skull is available on all difficulties, it is a sort of "trick skull", to make you think you've obtained the skull of the level, since every other level (excluding the Heretic, which is an opening cut-scene) has one, obtainable on Legendary only. So, it is meant to stop you from getting the IWHBYD Skull. Another possibility is that the scope is meant to stand for the word "Look" and the four grenades stand for the word "For" which could make the message "Look for Skulls" ("Skull" is in reference to the Blind Skull). Also, after getting the Skull, walk back a bit and activate your flashlight. A circle of light on the ground where the sniper scope is appears (it looks quite a bit like the Marathon symbol, this will not work if you restart the level or save and quit). Also, this Skull is often used for making machinimas, as you cannot see yourself. In contrast to the Active Camouflage, in which there is a slight shimmer, there is perfect invisibility for the Blind Skull, thus increasing its usefulness. Also with this Skull you will not have a flashlight on the level Outskirts and possibly all levels.

Status: Confirmed

Catch
Level: Metropolis

Directions: Right after you exit from the underground highway, you'll come to a large open-air circular area with a handful of Jackal Snipers and some Elites. The quickest way to get safely to the Skull is to get the next checkpoint by jumping into the Warthog and letting the Marine drive you to the next area. Jump out of the Warthog and backtrack to the large room, and clear the area. Or you can get your Warthog from the bridge and just run right through the platforms and the other part until you reach the place where you find the Wraiths attacking the building where the Marines are (but you don't have to fight them) and then go back and the enemies will be gone when you go back. You will see a large semi-circular beam going from one of the main platforms that goes from the ground up to the top of the two towers. Do a Grenade Jump at the bottom of this beam and walk all the way to the top. Jump over to the ledge of the left tower. Walk to the end of the ledge and you will find the Catch Skull. The Sputnik Skull may be helpful if you have trouble Grenade Jumping.

Difficulty: Legendary

Effect: A.I. will throw more grenades. Also, everybody (allies and enemies) will drop two grenades.

Extra Information: It is wise to have this Skull on in Flood levels, since Flood do not throw grenades. This Skull is also slightly tinged orange where the other Skulls are not.

Status: Confirmed

Envy


Level: Delta Halo

Directions: Progress through Delta Halo until you come to an area with a large central structure that has a multitude of columns. This is the area where Cortana tells you that they are all pouring out of the middle. When you first get into this area, you have to go left, and there is a ramp on the left that goes up and then back down. Get on this ramp and continue up the wall until you are on the landing where there will be (or used to be) some Plasma Turrets. Follow this landing all the way to its end, and you'll see a door that is blocked off by a large stone. Jump on top of the stone, and jump again to get on a thin ledge. Make sure you're up against the left wall, and Grenade Jump up to the top of the wall to your left. Once you're on this wall, you'll see that the right wall ends and there is some earth behind it. Jump onto the dirt, and follow the stone wall all the way to the top. When you're on the top of this wall, you can look down towards the center and you should see two Stealth Elites repeating their "angry stance" towards each other with the Envy skull between them. (Note: They will not attack you, even if you shoot at them. But if they are killed they will fire their weapons randomly before they hit the ground, which can hurt you).

Another way of getting the Skull is to grenade the stone away from the door. For that, you'll need all the Fragmentation and Plasma Grenades you can carry, sometimes even more. Throw each of them into the corner behind the stone. Every time a grenade explodes, the stone will move a little. You'll never get it fully out of the way, but after about eight or nine grenades, there will be enough space to go through the door. Alternatively jump on the rock and throw one Plasma Grenade in the corner behind the rock. This should move it enough so that you can drop into the crack and melee the rock until the doorway is clear. If not, throw a couple more grenades. It leads you up a ramp and into a room open to one side where you'll find two dead Grunts along with two Energy Swords (an Easter Egg which implies that these two Grunts accidentally killed themselves with the Swords). If you leave that room, you'll be on the platform with the two Stealth Elites.

Difficulty: Legendary

Effect: The Master Chief now has an Active Camouflage device just like the Arbiter's. However, there is no visible timer, so remember: five second cloak with ten second recharge on Legendary (the recharge and cloak times are shorter and longer respectively on easier difficulties). To fully exploit the effects of this Skull, execute the permanent invisibility glitch.

Status: Confirmed.

Famine
Level: The Oracle

Directions: After you get off of the slowly descending elevator, you will come to a hallway where you see a handful of dead bodies. Continue into the next room, and you will be on the second floor of a room that has a lot of glass windows. When you enter this room, look to the right, and find the third pane of glass. It should be to the right of a wall that has some Flood guts splattered on it. Shoot out this window, and the windows directly across the room. If you look below you, you will see a platform that has four tall posts. On the far side of the room there is a column that is right in between the two windows on the far side of the room. Turn on your Active Camouflage, and jump to the center platform. Jump on either of the posts on the far side of the platform and jump to the column between the windows. Make another jump through the window you shot out, and make a left. Walk all the way to the end and you'll find four Elite Combat Forms convulsing on the floor, with the Famine Skull in the middle of them. Sometimes, the Combat Form nearest to the battlefield stands up, but it does not attack.

Difficulty: Legendary

Effect: All dropped weapons have half ammo. Weapons that spawned on the floor or spawned with are unaffected.

Status: Confirmed

Ghost
Level: Uprising

Directions: Immediately after the armory room that is full of Covenant and human weapons, there is an L shaped room. Grenade Jump, using a Ghost, up to the rafters of this room, and you will find the Skull over a doorway. Or, if you are playing co-op, get a box from the weapon room, and have one player stand on the box, then have the other player stand on the first player's head, have player two Crouch Jump on to the ledge and grab the skull.

Difficulty: Legendary

Effect: A.I. characters will not flinch from attacks, melee or otherwise.

Status: Confirmed

Grunt Birthday Party
Level: The Arbiter

Directions: The very first time you get a Banshee, fly down. Below you is a large beam-like structure (not to be confused with the one directly below you that turns and goes vertical) running from the arm of the station you just came out of to one exactly like it on the side opposite. Below this structure are three cylinders hanging down, with cylinders of light shooting out of the bottom(and the sides). They look like they are what keep the station afloat. If this explanation is too vague, they are the absolute lowest parts of the station. Now go to the middle engine and land on the top part of it. This and the other engines connect to the large structure mentioned earlier. The tops of the engines come up to meet the structure at an angle, where this angle is under the connecting structure and coming up to meet it, there is a place to walk (like being under a bridge). Under one side you will see the six Heretic Grunts dancing in a circle around the Skull. If you want to see the effects immediately, headshot one of the Grunts (the others won't react in any way), and his head will explode!

Difficulty: Legendary

Effect: Headshots turn into Plasma Grenade explosions. You must first take down an Elite's shield for this to work on one. You also need to shoot Brutes and fellow Marines twice (if they don't have a helmet, you only need to shoot them once) in the head for this to work. You can also give a headshot to a dead body and it will still explode. This Skull doesn't affect Hunters, Drones or Sentinels. Keep in mind that the Flood's "head" is actually their sensory antennae, so you need to shoot them in the chest area. Note: you can combine this with the Sputnik Skull. This will make the explosions really powerful and amusing. (It is also A LOT easier to obtain with the Sputnik Skull.)

Status: Confirmed

I Would Have Been Your Daddy (IWHBYD)
Level: Outskirts

Directions: This is by far the hardest Skull to obtain. For the Skull to spawn at all, ALL previous checkpoints must be obtained. You can progress through the level normally to get IWHBYD, but the easiest way is as follows. From the beginning of Outskirts, run into the first hallway. A single Grunt will confront you. Kill it and then look overhead. You will see two lights on either side of the hallway. Jump on to one of them, and then crouch jump up to the higher platform. From there turn around and run along the thin ledge to the right of the alleyway below. Across from it, you will see another platform. Jump to it, then Grenade Jump or double jump onto yet another higher level. From there, look left and you will see a nearby rooftop, jump to it; go to the right and head down that alley, where you'll be able to jump onto the higher rooftop. Head to the top left corner (make sure you crouch when walking to the corner it helps) and wait for two checkpoints to pass. DO NOT MOVE FROM THAT SPOT UNTIL THEN! After the second checkpoint when the Pelican leaves, look to the right where the Pelican first spawned, and jump down onto the bridge below. Grenade Jump or jump on the banister and crouch jump onto the rooftop ahead and run forward over to above the little alley where your Marines wait for you to advance and wait for the checkpoint there. Backtrack to where you first jumped onto the rooftop in front of the bridge and head left towards where the Pelican leaves. Run along the rooftops until you reach the flat part of the bridge and jump down. Jump from the bridge into the alley below and run up the cement ramp. Turn right and you'll see some boxes. Jump onto them and get onto the roof to your left. From there, look right and jump onto THAT rooftop. Head to your left. You should be on the OTHER SIDE of the sniper alley, facing a small bridge where a Jackal Sniper spawns. Head to the right and you'll see two interconnecting balconies. Head to the one furthest from you, and go through the door. If you've done things right, you'll see the Skull between a sniper and some ammo. Be warned, the Skull will ONLY appear if you've obtained ALL PREVIOUS seven CHECKPOINTS ! There is also a checkpoint OVER the Skull's room, so wait to get it before you go inside. If the Skull does not appear, then simply revert to last checkpoint and try again. If you want to save the Skull, (in case you fail in the fight with the Elites) you should exit the room and proceed to get another checkpoint. Save and quit. Restart and go back to room with the Skull. It will always be there. When you grab the Skull, you'll be transported into the alley. You'll have only a Plasma Pistol, and must fight off seven waves of Ultra Elites (wave one starting with one Elite, wave two with two Elites, and so on). Note: this is a LOT easier with the permanent invisibility glitch. If you die in the alley with no checkpoint after the checkpoint in the Skull room, there will be several white flashes, you will be reverted to the checkpoint in the Skull room, the Skull will disappear sometimes and will not take effect. Also, if you attempt to escape the alley, you will get teleported to the Elites' position and lose all your collected weapons. Once you kill all seven waves, the Skull will become active. Note: If you get a checkpoint while fighting the Elites, save and quit. You will restart where you saved and then you can continue killing them. Saving here will enable you to load the IWHBYD effect (by killing the remainder of the Elites) after the Xbox is turned off, although the actual Skull will not be reloaded.

Difficulty: Legendary

Effect: Fight seven waves of Ultra Elites (a reference to Bungie's favorite number, "7"). The rarity of combat dialog is changed, rare lines become far more common but common lines are still present at their normal rate.

Status: Confirmed

Trivia: The Skull is named after a Sergeant Johnson quote sometimes heard in Assault on the Control Room: "I would have been your daddy, but the dog beat me over the fence!" Sergeant Stacker also occasionally says this on the Silent Cartographer. The first chapter of Assault on the Control Room is also named "I Would Have Been Your Daddy...". IWHBYD may also refer to it.

Iron
Level: High Charity

Directions: When you enter the final (the second) large Gravity Lift (do not confuse with smaller ones throughout the level), look up. A Skull will pass through you extremely quickly so you must start holding X a bit before you actually pass it to grab hold of it.

Difficulty: Legendary

Effect: When playing co-op, if either player dies the game restarts you at your last checkpoint. The effect resembles the effect already in place on Legendary difficulty, making it a somewhat redundant Skull.

Status: Confirmed

Mythic
Level: Sacred Icon

Directions: There is a semi outdoor area which has the same type of area right next to it. There is an Enforcer in front of each one. Go past this area and down the piston and you'll be in a very dark and dank Flood infested area. There's a stack of six or seven boxes as you enter the room. Use them to jump up to the landing above. There are a handful of alcoves on your right hand side. The Skull is in the third alcove, floating above a dead human Flood.

Difficulty: Legendary

Effect: Enemies have more health and shielding, and are therefore harder to kill. Note: health and shielding increase more as the enemies rise in rank. A red Grunt, will not gain as much health as a white Grunt. Similarly, a blue Elite Minor will gain a small bit of health, but an Ultra Elite will gain a ridiculous amount of both shielding and health, to the point that a Plasma Pistol overcharge won't drop their shields even halfway. Besides that, it also makes your allies gain a small bit of health, and the Skull will make allies immune to being meleed.

Note: For those who like a challenge, combine with the Thunderstorm Skull.

Status: Confirmed

Sputnik
Level: Quarantine Zone

Difficulty: Legendary

Directions: This is one of the easiest Skulls to obtain next to to the Blind Skull. At the start of the level, look directly behind you for an Elite. Slightly further to the right of it is a tunnel. Go through the tunnel and continue walking straight until you pass a bridge, which is to your right. Beyond the bridge there is a narrow ledge jutting out of the cliff face ahead. Jump onto this. Hug the wall (Just enough room for you to walk) until you get to the end of the cliff, and you will see the Sputnik Skull floating in the air.

This is arguably the most popular skull in Halo 2, as players like to have a lot of fun making things fly around and going on "vacations". A lot of glitches involve the use of the Sputnik Skull.

Effect: The mass of certain objects is severely reduced, making them fly further when smacked with a melee hit, or when they are near an explosion. Weapon damage seems to have strengthened slightly. It also has the added effect of making enemies turn around when you hit them, allowing you to kill them in two hits. With the Sputnik Skull's effect in place, players can reach nearly impossible places and much higher altitudes using Grenade Jumps. Also, your melee has strengthened force. This Skull is one of the ways to obtain the Scarab Gun and is a key component if you want to get the Soccer Ball Easter egg.

Status: Confirmed

Thunderstorm
Level: Cairo Station

Directions: In the large room after the armory, you need to use a Crouch Jump to get onto a light fixture on the right wall (right of the room when you enter) and then jump from there onto the higher area. There is a series of diagonal beams. Walk up one near to the end of it and use it to Crouch Jump onto one of the rails. You can fall between the rails, so be careful. Once on the rail, walk down it until you can jump onto the highest platform. Then melee the trashcan away from the wall a few times, the Skull is right behind it.

Alternate Directions:It is possible to Grenade Jump up to the platform if you can't stay on the rails. The Sputnik Skull helps a lot here, but it's possible without it. Just get on the ground near the platform the Skull is on and Grenade Jump. You also don't need to melee the trashcan out of the way, but it will reveal a interesting hidden object. Near the Skull is a burning cigar that looks like a Sweet William Cigar, the type that Sergeant Johnson is seen using.

Difficulty: Legendary

Effect: Elite Minors and Majors become Ultras, Grey Stealth Elites become Brown Stealth Elites and Brown Heretic Elites become Gold Heretics. Rangers, Honor Guards, Councilors, Zealots and Spec-Ops Elites are unaffected. Grunts (Except Gunner and Spec-Ops), Jackals (Except Snipers), and Brutes (except Honor Guards) become their highest rank. All Elite Combat Flood forms have shields and all Sentinels are Majors (Except for those in The Arbiter and The Oracle).

Status: Confirmed

Note: Any enemy units that have spawned, previous to you acquiring the skull, will remain at the same rank they spawned as.

Unnamed Skull
Level: The Armory

Directions: At the beginning of the level, after you power your shields for the first time, Sergeant Johnson shows up on an elevator. Wait in the room until Johnson starts berating you, telling you to get into the elevator. You MUST wait for him to say "Would it help if I said please?" (this takes approximately four minutes and forty seconds). Once he says this, get in the elevator, and go up to the tram. Get on the tram, and face towards the INSIDE of the building. Press up against the glass doors towards the inside of the building. You should hold X down, and you should pick up the Skull. It's on a stack of crates, near the end of the tram ride.

Difficulty: Legendary

Effect: The Unnamed Skull strengthens the Artificial Intelligence of both allies and enemies. They will now notice the slight shimmer of active camouflage, shadows, the sound of reloading or drawing a weapon, footsteps, etc. All computer controlled characters have better accuracy and are much less likely to kill themselves or their teammates (you, for example) with the Rocket Launcher/Fuel Rod/Brute Shot. Status: Confirmed.

Trivia

 * Halo 2's Skulls are the only ones to have 'fun' surroundings. An example being the Heretic Grunts dancing around the Grunt Birthday Party Skull. This is a distinction that is absent in Halo 3.
 * If you want to have access to any Skull any time you want you can follow these steps.
 * 1) Set up a new profile with the name of the desired Skull (so you know which profile is which)
 * 2) Go to the level that has the desired Skull.
 * 3) Play through on Legendary until you get a checkpoint just before the Skull.
 * 4) Save and quit. Now when you want the Skull you can go back to that profile, pick up the Skull, and exit out. Then just go to another profile and enjoy. It is much easier done if you obtain the Envy Skull first. NOTE: If you get a checkpoint after picking up the Skull DO NOT save and quit just turn your Xbox off and try again.
 * The file in the Halo 2 code nicknames the Unnamed skull 'Whuppopotamus', although no name for the Skull appears in-game. It has been called the "Monkey Skull", "Hide-and-Seek Skull," "Please Skull," "Find Me Skull," and "Cowbell Skull", though, but still nothing official.
 * The permanent invisibility glitch can help you find the skulls the Master Chief can obtain.
 * The Skulls are used to vary the game a little bit, and the effect of them will go away once you turn off your Xbox, or go to the dashboard on your Xbox 360 (or, in Halo 2 Vista, quit out of Halo 2.)
 * The IWHBYD Skull is actually easier to complete with the Envy Skull and activating the permanent invisibility glitch, especially against the seven waves of Elites.
 * The Blind Skull, the Sputnik Skull and the Unnamed Skull are the easiest to get because you don't have to fight any enemies to get them.
 * The Assassins Skull is found in any difficulty except it won't give you the effect, but it could still be used as a melee weapon.
 * There is a small symbol on the back of each Skull. For the Oddball, it is a miniature "Bulls-Eye". At some point, there are numbers found on top of every Skull you find.
 * Only the Grunt Birthday Party, Famine, Envy, and Assassins have characters around them that relate to the name/effect.
 * The Halo 3 skull, Cowbell, practically has the same effect as the Sputnik Skull from Halo 2 (explosive force increased), it has just been renamed.
 * The Halo 3 skull, Cowbell seems to have gotten it's name from one of the nicknames for the Unknown Skull in Halo 2.
 * A Skull's melee power is a little less than equal to firing a round of an M90 Shotgun. However, if you jump and, as you are coming down, hit an enemy, they will die.
 * During the opening cutscene on the level Gravemind, when the Gravemind reveals the High Prophet of Regret, a Skull similar to these is fused into his tentacle.
 * If the Sputnik Skull is activated during the opening cinematic of Outskirts, when the Scarab walks on a truck, it will lift from the ground.
 * The Skulls are supposed to be Captain Jacob Keyes' Skull from Halo: Combat Evolved, as they all have the slot in the Skull for the neural implants .(although this is general issue for UNSC personel)
 * The Sputnik Skull can also be useful in obtaining the Scarab Gun on Metropolis and the giant Soccer Ball, which is on the same level.
 * With the Mythic Skull on, a Brute and an Elite Major Domo can survive a Plasma Grenade stick.
 * Outskirts is the only level where there is more than one Skull.
 * Most Skulls have a poster with a scary skull above them and a number seven. When you use a flashlight, turning it on only makes some part of the poster unseeable or translucent. Switching it off allows you to see it clearly. For the IWHBYD skull, the number 17 appears above it and if you pick up the sniper rifle next to the skull and reload with it, you will have 17 rounds (plus the 4 in the chamber already).

Related Pages

 * Halo 3 Skulls