Therion is a pioneering Swedish symphonic metal band founded and led by multi-instrumentalist, composer, and vocalist Christofer Johnsson. Originally designed as a death metal band, Johnsson took the name from the Celtic Frost album To Mega Therion. By the time they issued their third album, 1993's Symphony Masses: Ho Drakon Ho Megas, Johnsson remained the only original member and Therion's sound began an evolution toward doom metal with electronic and avant-garde elements. For 1996's Theli, the band's sound adopted Persian modes and scales, and was performed by a rock quintet, two classical choirs, a simulated orchestra, and an army of keyboards. 1998's Vovin found Johnsson recording with completely different musicians than he toured with, while 2001's Secret of the Runes was based on lyric themes from the nine worlds of Norse mythology.
Johnsson inexplicably added covers of the Scorpions' "Crying Days" and ABBA's "Summer Night City" to that concept album. In 2004, the band released Lemuria and Sirius B simultaneously -- 171 musicians participated in the recording sessions, including the City of Prague Philharmonic Orchestra and a 32-voice classical choir. 2007's conceptual Gothic Kabbalah featured five vocalists -- three females and two males -- amid their most ambitious musical settings and prog rock production tropes yet. 2010's Sitra Ahra was a perfect meld of Therion's classical aesthetics and doom metal. 2012's Les Fleurs du Mal consisted of covers of French chansons and pop songs performed in the band's symphonic style. In 2017, Therion issued the three-hour rock opera Beloved Antichrist. They followed with the first volume in the Leviathan project in 2021. Each album sought to reflect the different sonic eras in the band's history while delivering all new material. Leviathan II followed in 2022.
In January 2021, Therion issued Leviathan. Written by Johnsson and Vikström, it was conceived as a trilogy to give fans a solid, end-to-end trilogy of "Therion hit songs," even though all the material was current. The set's personnel lineup featured the return of Koleberg on drums, and included a guest vocal appearance from Nightwish bassist and vocalist Marko Hietala. Leviathan II, issued in October of the following year, revisited the mystic, melancholic sonic aura of their groundbreaking 1998 work, Vovin, while the projected third entry, plotted for September 2023, would focus on the band's "braver orchestral songs."