Dissidia Duodecim Final Fantasy EXTRAS Chaos: Last Battle

Chaos Last Battle is the 22nd track off the 2nd disc the official Dissidia Final Fantasy Original Soundtrack, and was composed by Takeharu Ishimoto and was arranged and performed by the band Your Favorite Enemies.
The song (Chaos Last Battle 1) itself is actually taken from another song by Your Favorite Enemies entitled The Messenger. Lyrics from The Messenger are incorporated into Cosmos.
Although The Messenger itself doesn't play or appear in-game, the original song was featured on the official Dissidia Final Fantasy Original Soundtrack, track 25 on the 2nd disc.