Fierce Battle

 is Track 10 on the Xenosaga THE ANIMATION Original Soundtrack. It plays in the following scenes:
 * Gnosis gate out around the Woglinde in Episode 1.
 * The 100-series Observational Unit Realians aboard the Durandal activate the Hilbert Effect in Episode 4.
 * The Durandal crew reacts to the Gnosis gate-out around the Kukai Foundation in Episode 9.