What we brought for Lord of Admirals and his last warriors were the Composers. These large, ugly machines had originally been designed by Builders in a failed attempt to attain immunity against the Flood. Composers broadcast high-energy fields of entangled sympathies to gather victim mentalities—essences—and then translated them into machine data. In the original scheme, new bodies were constructed, and the subjects’ essences were imprinted over them—minus any trace of Flood patterns.

Halo: Silentium Ch 3