Core room antechamber
From Halopedia, the Halo wiki
The Core Room Antechamber was a massive chamber located in the center of the Forerunner construct Onyx, serving as the only enterance to Shield World. It was extensive, and had a bright white glow.
Following the activation of the Halos, the Core Room Antechamber would become accessable via several teleporters on the Forerunner ruins around the world. They would transport the user to the Core Room Antechamber, which contained a large hill made of ascending steps. Gradually, the steps would descend, making the hill shorter and shorter until it was level with the ground. At this point, the entrance to Shield world, which was at the center of the hill, would close forever.
This room was the site of a huge battle between the Spartan-IIs and -IIIs under Spartan-051 (Kurt) and the Covenant forces under Voro 'Mantakree. It was destroyed when Spartan-051 detonated FENRIS Nuclear Warheads in an act of self sacrifice, killing the Covenant.
