Energy core

Energy Cores are Forerunner devices consisting of three oversized Power Cores in the shape of a three-sided pyramid that project streams of energy into its hollow center. The three streams combine to form a pink ball of energy that is maintained in stasis. The purpose of these devices is unknown, although they could be a battery-type energy source. They are highly explosive (four times the power of any other explosion alone) if damaged or rammed violently but can be pushed easily.

They are found in Forerunner installations, such as the Halo Array. Their only appearance to date is on the Halo 2 Multiplayer map Containment, which is a small section of the Containment Zone surrounding Installation 05's Library.

Trivia

 * Pure energy does not exist. Energy is a property of a system, more specifically, the potential to do work.