I think the song is about the angel being transformed into a wolf.
The angel is a symbol of innocence when talking Nightwish.
The wolf is a symbol of the beast which represents bestial freedom and some other things. Also note "the beauty of the beast" often used by Nightwish. This might help to understand the full symbolic meaning of the beast as it is a little hard for me to put into words.
The transformation from angel to wolf might represent growing up in the "right way" as Nightwish sees it.
I think the song is about the angel being transformed into a wolf. The angel is a symbol of innocence when talking Nightwish. The wolf is a symbol of the beast which represents bestial freedom and some other things. Also note "the beauty of the beast" often used by Nightwish. This might help to understand the full symbolic meaning of the beast as it is a little hard for me to put into words. The transformation from angel to wolf might represent growing up in the "right way" as Nightwish sees it.