Invasion

Invasion (called Infiltration on the Revival disc) is Disc 1, Track 18 on the Xenogears Original Soundtrack and track 19 on the Xenogears Original Soundtrack Revival Disc -the first and the last-.

It plays as the area music in Nortune (except for the Battling Champ's room and Kaiser Sigmund's rooms), in the Bledavik waterway, in Fatima Castle before the party reaches Nisan, in the land-dwellers' quarters areas in Solaris, and in Solaris after Citan removes the party's limiters. It also plays in the following cutscenes:
 * Bart and his crew prepare to capture Shakhan after entering Fatima Castle through the waterway.
 * Fei meets in Nortune.
 * Fei and Rico temporarily part ways after leaving the D-Block sewers.
 * Hammer lets the party know about the Goliath.
 * The party looks over Nisan, which is currently overtaken by Shakhan's soldiers.