Skulls are gameplay modifiers as seen in Halo: MCC, Reach, and Halo 4. They’ve been an important part of Halo and can be found scattered throughout the campaign missions. Once acquired, you can enable skulls/modifiers from the level select menu for hilarious or serious results.

Similarly, Halo: Infinite features 12 skulls, and 5 of them are missable and the rest of them can be found while exploring the semi-open world of Infinite.

Halo Infinite Skulls

• Boom – Doubles explosion radius (missable). In the first mission – After getting your first UNSC Audio Log, head straight into a large room with containers near a moving platform on the right side of the room, jump on one of the platforms, and wait for it to rise up to grab it. 

• Cowbell – Acceleration from explosions is increased (missable).
  In the second mission – After you obtain The Weapon, Inside a blue hallway, once you’re done fighting Grunts and Jackals, Master Chief will start seeing visions of his childhood and other test subjects (children). The Cowbell Skull is found inside a hatch in the ceiling, use your grappleshot to reach it.
  
• IWHBYD – Rare combat dialogue becomes common.
  On the first Island – The Tower – simply climb the top of The Tower either by using your upgraded grappleshot or flyable vehicles like a Banshee or Wasp. You’ll find it right on top of a container.

• Blind – Hides HUD and Weapon.
  On the first Island – Between two mountains, you’ll come across dead marines and a glowing blue substance where you’ll be ambushed by a Banished ship. From the Marine’s corpse, jump down and head right towards the inner side of the cliff where you’ll find the skull.

• Catch – Enemies throw and drop more grenades.
  On the second Island –  Near two circular pathways (upper side of the map), you’ll find multiple Brutes and Hunters guarding a tree bark. Kill them to get the skull hiding inside the bark.
  
• Fog – Disables Radar. On the second Island – from FOB Alpha, head towards the hexagonal-shaped platforms along the edge where you’ll come across a doll. Look up and use the grappleshot until you reach a hidden opening where you can find the Fog skull and weapons.

• Famine – Weapons dropped by enemies have half the ammo than usual.
  On the fourth Island – Using a Banshee or a Wasp, head to the small island next to the Beacon on the right side of the map. Look for a gold-colored elite’s corpse and find the skull by listening for its noises which should be audible enough.

• Black Eye – Shields only recharge when you melee enemies. On the fourth Island –  Inside a small opening under a waterfall between Riven Gate and FOB Kilo. You can find the opening by scanning the area in front of the waterfall.
• Thunderstorm – Upgrades the rank of most enemies.
  On the fourth Island – right on top of a pillar near the Northern beacon where you’ll also find another collectible (an audio log), along with a sniper.
  Use the grappleshot to make your way towards the skull.
  
• Mythic – Enemies are tougher (missable).
  In the 11th Mission – Inside the room after the grav lift, grapple onto one of the pillars with golden accents on it just before it turns then grapple once again above you into a dark hatch. Proceed towards the hallway to grab the skull.
  
• Grunt Birthday Party – Headshotting grunts will result in confetti and cheers (missable).
  In the 12th Mission – in the large room with a terminal which is adjoined by two light bridges. You’ll want to obtain a power seed from one of the side which isn’t connected by the bridge and transport it to the other side which also isn’t connected by a bridge either. Continue forward and follow the objective after you place the power seed into its slot.
  After your conversation with The Weapon, proceed to the next room and jump on top of the platform by climbing on top of the arched structure. Once you enter the hidden room, kill the invisible elites and grab the skull.
  
• Bandana – Unlimited ammo, grenades, and cooldown (missable).
  In the 15th Mission – Ignore the Sentinels when they attack you, proceed through the level, right at the end when you have to get into the elevator, there will be a room next to it. Cross the bridge where you’ll find the final skull.

Recommended | HALO INFINITE ALL MISSION 2 – FOUNDATION COLLECTIBLES GUIDE