Forerunner energy potential 1

Now there was a crueler irony: Vil lived on a great chunk of what had once been Janjur Qom. It was the homeworld of the San’Shyuum, the homeworld of those who had wiped out so many Sangheili. The great mass of stone and soil, about two mountains worth, taken up by the Dreadnought when it arose from Janjur Qom, had been removed from the keyship and formed into an asteroid; it was to be the foundation of the true pedestal of High Charity. And already there were warrens dug into it, sealed off subterranean fortresslike structures, airtight and almost self-sufficient, where lived Sangheili serving as guards, protectors of the San’Shyuum.
(Halo:Broken Circle; Ch.5)

A world spread out below Mken. Clouds spiraled around a giant crater, the immense blue sea known as the Great Apothtea; the dark green of vegetation carpeted much of the main continent; outer regions were more rugged. Mken recognized a number of features from his studies of the old holograms. Was that not Zelfiss, where the fabled fortress of Granduin, undermined by the Stoics, had crumbled into the sea? And the crater— it was once the resting place of the Dreadnought, partly submerged below Apothtea’s surface, but it was now the mark of the great ship’s ascension; it was the scar where the Reformists had taken a god’s fistful of the world as the mountain-high vessel rose to meet the stars.
(Halo:Broken Circle; Ch.6)