Conversation so far:
Is Sonata Arctica's Unia and The Days of Grays a musical band?
Unia, is the fifth full-length studio album by the power metal band Sonata Arctica. The Days of Grays is the sixth full-length studio album.
Wsa the Sonata Arctica album, Unia a hit?

Question: Who were the artist?
Self-contained rewrite: Who were the artist in the Sonata Arctica album, Unia?