Welcome to Halo Answers. What would you like to know?

They're Easter eggs put in Halo on purpose that turn on certain effects when activated. In 2 & 3, you have to find the skulls on their corresponding level. In Reach, they're all there already, taking out the fun of finding them.

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.