Therion are a Swedish symphonic metal band led by Christofer Johnsson. Originally a death metal act, they evolved toward doom metal by 1993's third album Symphony Masses: Ho Drakon Ho Megas. They adopted Persian modes and scales for Theli (1996), performed with two choirs, a simulated orchestra, and an army of keyboards. Secret of the Runes (2001) was based on Norse mythology. Simultaneous releases Lemuria and Sirius B (2004) involved 171 musicians, Gothic Kabbalah (2007) featured five vocalists, and Sitra Ahra (2010) melded classical and doom metal. The three-hour rock opera Beloved Antichrist (2017) included no less than 29 vocal characters. In 2021, the band issued Leviathan, the first of a projected three-volume "sonic" retrospective consisting of all new material. Leviathan II appeared in October 2022, while Leviathan III, the trilogy's final volume, appeared in December 2023.