Therion is a Swedish symphonic metal band founded by Christofer Johnsson in 1987. The word 'therion' comes from the Greek therion (θηρίον), meaning 'Beast,' i.e., that of the Christian Book of Revelation. However, the band's name is a homage to the Celtic Frost album To Mega Therion. Beginning as a death metal band, they later turned to combining orchestral elements with their metal music, employing heavy use of choirs and classical musicians, not only as additions to but also as integral parts of the composition. Therion is the first metal band with fully live orchestra featured. It is also the band which originated, popularised and influenced the symphonic metal genre, cited as 'the most adventurous metal band at present'. Because of these extents they take in conducting their music, they have been dubbed as 'Opera Metal'.