Rage, Darkness of the Heart

Rage, Darkness of the Heart is Disc 2, Track 11 on the Xenoblade Original Soundtrack. It plays during these cutscenes:
 * The entrance to the Weapon Development Lab is blocked off by debris during the Mechon assault on Colony 9
 * Metal Face leaves Colony 9 after the second battle
 * Otharon telling the party what happened to him and Gadolt in the Ether Mine
 * Xord's destruction after the second battle on the in the Ether Mine
 * Before the battle against Gold Face and in the Fortress Depths of Galahad Fortress
 * Meyneth proposing to break Gadolt's curse after his first battle at the Shrine Transporter in Agniratha
 * Egil moves to the Mechonis Core after the battle at the Meyneth Shrine in Agniratha
 * Shulk telling Egil that he won't kill him after the battle in the Mechonis Core
 * Lorithia turning Kallian and the other High Entia into Telethia after the battle against the on the Junks Deck
 * Dickson's death on the on Prison Island

It also plays in Xenoblade Chronicles: Future Connected, when Gael'gar blows up Teelan's laboratory.