KING UNDER THE MOUNTAIN
From Halopedia, the Halo wiki
KING UNDER THE MOUNTAIN is the nomenclature used to refer to any files pertaining to the planet Onyx. It was assigned on March 6, 2525 by Vice Admiral Margaret O. Parangosky. It was also the name of a file on Colonel James Ackerson's computer at CASTLE Base on Reach, containing files related to Onyx, and other material closely related to the Forerunners as well. The other file on Ackerson's computer was called S-III.
The KING UNDER THE MOUNTAIN file contained:
Due to the order that all materials and files relating to Onyx was to be redesignated under KING UNDER THE MOUNTAIN, it is possible that Ackerson was using the Forerunner data in the file to find technology to use against the Covenant or for his own personal means.
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