Set a Fire in Your Heart
From Halopedia, the Halo wiki
The track opens with strings, quickly followed by percussion. At 0:13, double bass enter with Escharum's theme. Percussion return, building up a tribal rhythm, with strings accompaniment. The melody slows down briefly, but returns as high strings play the Halo Theme Gregorian chant, interjected with excerpts of Escharum's theme between its verses. The track ends with the piano playing the fanfare of Finish the Fight (from Halo 3: Original Soundtrack).