The battle of your soul

the battle of your soul is Disc 1, Track 7 on the Xenosaga III: Also Sprach Zarathustra Original Sound Best Tracks album. The beginning of the OST version of the piece never plays in-game during battles (the in-game track starts at 0:12 in the album version). However, the beginning (from 0:00 to 0:24) is included as part of maybe tomorrow~ending medley.

It plays as the battle theme for the following bosses:
 * over Rennes-le-Château.
 * in Rennes-le-Château.
 * in Rennes-le-Château.
 * Voyager in the Elsa.
 * and Pellegri's Soldiers in.
 * and on Michtam.
 * on Michtam.
 * Ω Id in the CAT Testing Ground.

In Project X Zone
A remix of the battle of your soul was made for Project X Zone. It plays at several points in Chapter 19, 'Thus Spake Eternity', such as when KOS-MOS arrives on the scene at the Woglinde.