Desolation

Desolation is Disc 3, Track 3 on the Xenoblade2 Original Soundtrack. It is a version of Walking With You with many instruments replaced by a piano. It plays in the following cutscenes of the main game of Xenoblade Chronicles 2:
 * Rex and Mythra drive back Malos and Akhos at the Olethro Ruins.
 * The party pays their respects to Vandham at his grave.
 * Tatazo prevents Poppi from destroying Lila, who then undoes Bana's control over her.
 * Niall dies and is revived by Nia on the Titan Battleship in Indol.
 * Rex convinces Jin to stand down after fighting him in the World Tree.
 * Amalthus attempts to merge with the World Tree after being beaten by the party.
 * Malos gives his last words before dying.

It also plays in the following cutscenes in Xenoblade Chronicles 2: Torna ~ The Golden Country:
 * Lora and the rest of the party find the graves of the people of Torigoth.
 * Mythra sees Milton's dead body on the ship evacuating people from Torna.
 * Gort dies at the hands of Lora, Jin and Haze in Spessia.