Forerunner energy sources 1

As the reflective orb rotates beneath my ship, I see also the outstretched, feather-like plumes of vacuum energy pylons, drawing in the potential of an infinity of alternate realities ... aborting untold numbers of nascent universes to supply Requiem’s power. Strange that these cosmic deaths have never before struck me as cruel and futile. All of Forerunner technology has been made possible by drawing down vacuum energy. My own life, all that I know, arises out of cosmic predation.
(Halo:Silentium; Ch.33)

Then we were shunted out of planetary orbit and my family’s world grew small. Within a few more minutes, the Council ship harnessed a great deal of vacuum energy to flatten the curve of our stellar orbit, and the planet where I was born vanished completely.
(Halo:Cryptum; Ch.9)