I don't know why some other reviewers haven't liked this album - I loved it!
As the title suggests, it has a darker feel to it than previous albums, with songs like 'Symphony of the Night', 'Ophelia', 'Nightshade' and 'One Caress' giving it a dark fairytale-forest kind of feel. It's got a great range of moods and scenes: the title song has a beautiful, operatic, somewhat lamenting sound, 'Hell to the Heavens' is a powerful and (from what I can see) very popular track, 'Fading Earth' is a simple but very strong, catchy and melody-based song with an epic film-soundtrack sound to it, 'Galswintha' is a folk dance-type number with a danse macabre feel, telling a sort of dark legend, similar to 'Angel and the Ghost' (another melody and story based song), and 'Ophelia' is an epic highlight that encapsulates all elements from the album, with a powerfully catchy melody in the chorus, soaring vocals from Liv, some Krull vocals in the bridge, a strong structure and the story of Ophelia behind it. There are also quiet, hauntingly beautiful ballads in the form of 'Nightshade', 'One Caress' and 'Eileen's Ardency', the last of which is a folky, Shakespearian-sounding song with a steady, hypnotic beat.
My one criticism - and I know that not everyone agrees on this! - is that there's a lot of Krull's vocals, and some songs, like 'Hymn to the Lone Sands' and 'Maid of Lorraine', I feel are just back-and-forth alternating patterns of Liv and Krull, therefore lacking some structure. Personally, I prefer the tracks with as little growling as possible.