You want to know all the skulls? Here ya' go.
Skull: Hide N Seek
Level: Armory
Difficulty: Legendary
Word: None
Effect: Enemies become more aware of your location.
Location: The next skull can be found in the beginning of the “Armory” mission. When the Sargent appears, don’t get in the elevator quite yet. Wait for him to say: “Would it help if I say please?" Now get in and take the elevator up. When you get to the tram station walk to the opposite side of the doors and press up, while holding down the X button. The skull will be on a stack of green crates near the end of the ride.
Skull: Thunderstorm
Difficulty: Legendary
Level: Cairo Station
Word: Thunderstorm
Effect: Elites Brings out swords when punched
Location: It’s past the two loading docks past the armory type place and in the next big room. It’s in the very highest location in the room. It’s under a trashcan you can try to knock away the trashcan or just grab it through the trashcan.
Skull: Blind
Level: Outskirts
Difficulty: Any
Word: Blind
Effect: You will not be able to see your weapon, body, shields, ammo, or HUD.
Location: When you begin the mission, your vision will get blurry. When it returns to normal, you will see a blinking door. Enter it, then stop. Look up to see a fluorescent light over the door you just used, and another one on the opposite wall. Jump and duck at the same time to get on one of those lights. Do the same thing again to get onto the ledge next to the lights. Look to the left on the ledge and you should find a dark passage. Follow it to find some grenades, a skull, and a camera at the end. Take the skull and your HUD will disappear and the word “Blind” will be displayed. You will not be able to see your weapon, body, shields, ammo, or HUD. You can use the skull as a melee weapon, which does good damage to opponents. However, using a grenade, firing a weapon, trying to drive, or using a turret will drop the skull. Additionally, you can be a passenger in a Warthog and still keep it. To return to normal vision, save and quit the game, select the Cairo Station mission in campaign mode, save and quit the game, then return to the Outskirts level.
Skull: I Would Have Been Your Daddy
Level: Outskirts
Difficulty: Legendary
Word: I Would Have Been Your Daddy
Effect:?????
Location: Play the level on the legendary difficulty setting. The main thing appears to be getting the checkpoint just past the Pelican that picks up Johnson. This checkpoint spawns the sniper Jackals in “sniper alley”. The skull itself is in a room on a balcony. The room contains a sniper rifle and sniper ammo; it will also contain the skull. Picking up the skull will teleport you to the ground level and gives you just a Plasma Pistol. Elites will quickly attack you. Killing the last Elite will have the text for the skull flash. You have to kill all of the Elites to actually finish getting the skull. If you die to the Elites, and your checkpoint no longer spawns the skull, kill yourself four or five times to get pushed back one extra checkpoint. The skull should spawn for you again, and you can try the fight again. When you get the skull and kill all the Elites, the phrase “I Would Have Been Your Daddy” will appear.Note: This may require several attempts.
Skull: Catch
Difficulty: Legendary
Level: Metropolis
Word: Catch
Effect: everybody throws more grenades.
Location: Right after you get out of the sewers (Tunnel), there is a big area and 2 ghosts, kill every thing first, then go to the middle of it where you see a arc that leads up onto a building. Grenade jump by it to get enough height to start climbing it. When you get to the top take a left and hug the wall around the structure and the skull will be there.
Skull: Grunt Birthday Party
Level: Arbiter
Difficulty: Legendary
Word: Grunt Birthday Party
Effect: all headshots that kill the enemies will cause them to explode as if a plasma grenade were attached to them.
Location: Play the mission on the legendary difficulty setting. Proceed until you reach the first Banshee section. Immediately fly straight down to the bottom of the level. Search the cracks where the large cylinders connect to the station to find a circle of Grunts dancing around a skull. Get the skull and the words “Grunt Birthday Party” will appear. When you get the skull, all headshots that kill the enemies will cause them to explode as if a plasma grenade were attached to them. This works well if you aim for a Grunt in the middle of a group of enemies. Also, this may only work for projectile weapons, but does work for the Covenant carbine and the Covenant sniper rifle.
Skull: Famine
Difficulty: Legendary
Level: Oracle
Word: famine
Effect: Weapons have less ammo
After getting off the long elevator ride, you will come to a room where convent and flood are fighting below you, and you have to break the glass to get to where they are fighting. If you crouch/grenade jump up on the opposite side of where you came down, the skull should be up there.
Skull: Envy
Level: Delta Halo
Difficulty: Legendary
Word: Envy
Effect: You can now use active camouflage as Master Chief.
Location: Play the mission on the legendary difficulty setting. Continue until reaching the area during the “push through the covenant held ruins” phase where a landing zone for the Pelican to drop weapons must be cleared. When you reach the area where Cortana says “They’re pouring out of the center building”, note the plasma turrets along the borders. A short distance after the turret on the left side is the outline of a sealed door in a wall. There is a rock in front of the door. Jump on the rock, and then jump onto the ledge above the door. Next, jump to the ledge to the left. Then, grenade jump onto the building with the sealed door. On the roof of the building are two dancing Elites and a skull. Get the skull and the word “Envy” will be displayed. You can now use active camouflage.
Skull: Assassins
Difficulty: Legendary
Level: Regret
Word: Assassins
Effect: All enemies in the game are permanently cloaked.
Location: Play the mission on the legendary difficulty setting. Enter the structure after getting off the gondola. Jump on the large stone block to reach a ledge leading out to the Covenant turrets. Turn around and face towards the structure. Then, jump up to another level around the right side of the structure. Continue to find a skull on a ledge as you make it around. Take the skull and the word “Assassins” will be displayed. All enemies in the game are permanently cloaked.
Skull: Mystic
Level: Sacred Icon
Difficulty: Legendary
Word: Mystic
Effect: ?????
Location: There is a semi outdoor area where the flood is fighting sentinals including a large one it will have a lower level with a shotgun in one part and a Rocket launcher in another. At the end of this room there is a piston that you have to go down that leads to a dark room full of flood. if you look forward right when you go down the piston there will be a stack of 6 or 7 boxes on top of each other. Jump on top of them and get on the ledge. on the ledge there is 3 alcoves, in the last one farthest from you is the skull floting above a dead human flood.
Skull: Sputnik
Difficulty: Legendary
Level: Quarantine Zone
Word: Sputnik
Effect: Everything goes flying when punched or blown up
Location: From the start of the level, look to your left for an Elite. To the left of the elite there is a tunnel. Head into the tunnel and go straight until you reach a cliff. Now turn left and follow the cliff till you reach a rock wall. To the right of the wall and the cliff is a narrow passage, skull is at the end of that passage.
Skull: Anger
Difficulty: Legendary
Level: Gravemind
Word: Anger
Effect: enemies fire faster and are more aggressive
Location: Fight all the way through the Covenant City until you reach the outdoors. As soon as you are outside, stick to the right-hand side and walk along the wall. You should see a Covenant wall with a red rail on top of it. Jump up to it (crouch jump helps) and at the end there is the Anger skull in a small grav-lift.
Skull: Ghost
Difficulty: Legendary
Level: Uprising
Word: Ghost
Effect: ?????
Location: After the area outside where there is 2 Wraiths there is a armory room with human and covenant weapons inside. right after that room is an L saped room just before you get outside again. The skull is right above the door to the armory in this room. You cant see the skull because the triangle shaped light is blocking the view. To get the skull you have to use a hijacked Ghost and grenade jump of of the ghost to get up to it.
Skull: Iron
Difficulty: Legendary
Level: High Charity
Word: Iron
Effect: ?????
Location: On the final grav-lift on “high Charity”, look up. A skull will passby you. Hold X as it passes you to receive the status.
Skull: Black Eye
Difficulty: Legendary
Level: Great Journey
Word: Black Eye
Effect: Shield won’t regenerate, when you melee someone you get energy power back, so if you melee someone you get a little bit of shield. So you can get a bit at a time all the way to overshield!
Location: SGT Johnson will pilot the scarab and shoot at a building I am calling the Control Tower. If you take a banshee to the tower you will notice that, aside from where spires jut out of it, it has a round slope all the way around. If you take the banshee right up to the slope and as high as you can go, you can almost get over it. Here you must jump out of your banshee to land on the less steep part of the slope. If you turn your banshee to the side or all the way around, it may make it easier to land on the less steep part. Also, try to have your banshee land on a platform below, so you can use it to get back. Once you are on the slope, climb the rest of the way up it. If you are on the right of the door, then you have to jump onto the ledge next to the main part of the building, and then walk up a steep part in the direction of the door. Walk up that, then around and down on the other side. On this side (left of the door from scarab’s perspective) you can walk onto the hills and grass. You will notice several angled spires, some of which connect to the building. You must climb the one that is directly opposite the door you would use to enter the tower. It’s steep but you can walk up it. I suggest jumping while walking to speed up the process. At the top is a skull which gives you the “black eye” effect - you only recover shields by melee attacking enemies. This is only found on legendary. Reverse the process to get back to your banshee (hopefully) or just jump off a cliff and the effect will stay with you.