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Katy Perry is shining more light on her closely-guarded new album Prism.  

While closing the iTunes music festival in London on Monday night, the singer debuted the first ballad off the upcoming release, called "By The Grace Of God." 

In an earlier interview with "Billboard," Katy acknowledged that the song was written about her divorce from Russell Brand in 2011.  She gets more personal than ever on the new track, which includes lyrics about her "laying on the bathroom floor" and feeling that "the fault was all mine."  The singer revealed in the interview that she was deeply depressed following the breakup.  

Katy has also unveiled the full tracklist for the album's deluxe edition, which includes the already released "Roar," "Dark Horse" featuring Juicy J, and "Walking On Air."  Prism is out on October 22nd. 

Katy Perry Prism Tracklist: 

1) "Roar" 
2) "Legendary Lovers" 
3) "Birthday" 
4) "Walking On Air" 
5) "Unconditionally" 
6) "Dark Horse" (featuring Juicy J) 
7) "This Is How We Do" 
8) "International Smile" 
9) "Ghost" 
10) "Love Me" 
11) "This Moment" 
12) "Double Rainbow" 
13) "By the Grace of God" 
14) "Spiritual" 
16) "It Takes Two" 
17) "Choose Your Battles"