Therion is a Swedish symphonic metal band. It takes its name from the Greek word therion (θηρίον), which means beast, in reference to the "beast" of the Christian Book of Revelation. However, the band's name itself originates from the Celtic Frost album To Mega Therion. Therion was founded by Christofer Johnsson in 1987. 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's music takes its themes from different mythologies and is based on concepts ranging from occultism, magic and ancient traditions and writings. The majority of their lyrics are written by Thomas Karlsson, head and founder of the magical order Dragon Rouge, of which Johnsson is a member. The band has seen many changes in line-up and style throughout its history.