It's a pretty nice song. Just try not to let your opinion of the character influence your opinion of the song.

Translation of the lyrics (kudos to ismu34)

Transfiguration

Lululu･･Lululu･･

When you laugh in the devils smile, that shakes good and evil the urge that swallows up your very consciousness As I am satiated by the blood soaked meat ripped apart while still living, letting the desire control my body, I want to covet every bit, make it compensation for my bitterness

Awakening nature be released, now change into your terrible form and go to the forgetful sky Help! help! I can't go back

Cruel exterior the metamorphosis complete My heart's pattern is projected, the shadow of an image of sadness The freedom obtained by brown wings, the falling consciousness, fade The cursed black butterfly takes flight breaking the sorrowful silence

The waltz of ruin The rondo of insanity violent emotion stirred up and instinct takes over Save me! save me! Really, I want to go back

Lululu･･Lululu･･

Change into your terrible form and go to the forgetful sky Help! help!