Post-metal band from Turku, Finland. The band was formed in 2001 in Kokkola. Whilst their early works are hardcore/metalcore, their first album True Nature Unfolds has a strong sludge metal and doom influence and their second album Noir is more influenced by progressive and more dynamic sound. Their third album Providence, released in 2009, introduced clean vocals in their music. Apart from featuring female vocals on some of their early songs, they have used unexpected instruments, for example saxophone, cello, flute and English horn. Callisto's short and cryptic lyrics contain Christian themes and references.