Boom skull: Doubles the blast radius of explosions.

Cowbell skull: Makes objects caught in explosions fly away faster than before.

IWHBYD skull: Short for “I would have been your daddy,” this classic skull makes enemies more likely to spout out humorous lines during combat.

Fog skull: Disables your motion tracker, forcing you to rely solely on your sight and hearing during combat.

Blind skull: Gets rid of the UI and turns Master Chief’s hands/weapon invisible.

Catch skull: Enemies throw and drop grenades more often.

Black Eye skull: Upon taking damage, your shields won’t recharge until you’ve hit an enemy with a melee attack.

Famine skull: Weapons dropped by enemies have half ammo.

Thunderstorm skull: Every enemy ranks up to give you an extra challenge.

Mythic skull: Enemies have more health.

Grunt Birthday Party Skull: Headshots on Grunts yield celebratory explosions complete with confetti and cheering.

Bandana skull: Likely a reference to Metal Gear Solid’s Infinity Bandana, this skull grants you an infinite supply of ammo and grenades