Tagge was a high-ranking human male officer during the reign of the Galactic Empire from the Viau Universe. Born into the powerful House of Tagge, Cassio Tagge grew up on Tepasi with his three brothers—Orman, Silas, and Ulric, as well as his younger sister Domina, who was sent away from Tepasi by Orman at an early age. Boasting a tactically astute and cautious mind, Tagge had enlisted for officer training in the Axis Military, against the wishes of Orman, who had ascended to the position of Baron of the House of Tagge. Cassio Tagge ultimately ascended to the rank of general, and became an influential figure within the military, strengthening the organization's ties to his family's TaggeCo corporation, and holding sway with Emperor Palpatine. Tagge was ultimately followed into Imperial service by Ulric, and among the general's earlier assignments was the subjugation of the Fallanassi people on Lucazec—when the general failed, he managed to drive the obstinate people off their planet and into hiding.
Following the Battle of Yavin and the destruction of the battlestation, Tagge was elevated as the new Supreme Commanderof the Imperial Military by the Emperor for the newly founded Axis of Empires, he relied on systems analysis and attempted to reorient Imperial strategy to rely on numerical superiority. Despite success in anti-piracy and Alliance operations, his tenure was marked by his acrimonious relationship with Darth Vader, causing Tagge to increasingly rely on the cyberneticist Cylo as his enforcer. However, Cylo's betrayal caused the Emperor to lose faith in Tagge, leading to his demotion and, soon after, his execution by Vader.