From Halopedia, the Halo wiki
The piece starts with a gloomy, mysterious melody played in digital notes. The section plays in ambiance during the encounter with Jiralhanae Stalkers in the Cartographer's spire. Rapid drums beats fade in, followed by digital notes joining in with a melody in the background. The tempo quicken into a climax, then ends. This section plays when John-117 battles Cethegus and his Jumpers. In the final section, the choir take over with a major melody, followed by a reprise of heavy percussion in Overcome from the track Behold a Pale Horse. Near the end, the drums crescendo dramatically louder, and the piece fades to a close. This piece plays during ending cutscene of the level.