In a world where the metal band Dethklok reigns supreme, their frontman Nathan Explosion grapples with a vision urging him to embark on a daunting and mysterious quest. Amidst personal turmoil and conflicts within the band, Nathan learns about an ancient prophecy involving the Army of the Doomstar, a force that threatens to bring chaos and destruction to the world. With the weight of this revelation, Nathan must rally his bandmates—Skwisgaar Skwigelf, Toki Wartooth, William Murderface, and Pickles the Drummer—to confront this apocalyptic threat. The band's disarray becomes apparent as they struggle with their own demons and internal discord, but slowly, they realize the importance of unity.

As Nathan's journey pushes him to his limits, the band must navigate a series of challenges involving sinister cults, hidden secrets, and a mysterious figure linked to their fate. Each member must confront his own fears and shortcomings to unleash their collective power. Meanwhile, forces beyond their comprehension seek to exploit their weaknesses, testing their loyalty and resolve. Balancing the demands of their global fame with the urgency of their mission, Dethklok must come together to save not only themselves but the world. The unfolding saga tests Nathan's leadership and the band's resilience in an epic battle against destiny and despair.