The Demon Emperor is the supreme ruler of the demon race, a formidable antagonist known for his immense power and tyrannical reign over countless worlds. His background is rooted in a philosophy of absolute power, where strength dictates dominance and weaker races are subjugated without mercy. The demon race operates on a simple principle: power means everything, and a powerful race will conquer a weaker one to absorb its spiritual force, thus growing even stronger to conquer more civilizations. For thousands of years, the Demon Emperor has sat upon his throne, delegating the conquest of tens of thousands of races to his soldiers, who endlessly bring new subjugated peoples before him. His rule has turned the demon race into what many consider an invincible myth, having conquered millions of worlds and destroyed countless civilizations that dared to oppose him.

Throughout the story, the Demon Emperor serves as a major threat, representing the culmination of a long-premeditated invasion known as Demon War II. He embodies the ultimate challenge for the human race and its practitioners, who must band together to face this overwhelming force. His motivations are rooted in conquest and the expansion of demon dominion, viewing weaker beings as unworthy of standing before his throne. His personality is characterized by arrogance and a detached sense of superiority, as he has not left his throne for millennia, deeming it beneath him to personally engage in battles that his soldiers can handle.

Despite his fearsome reputation and the terror he inspires across the universe, the Demon Emperor is not an invincible force. In a pivotal turn of events, during the conflict known as Demon War II, the human race succeeded in breaking the myth of the Demon Emperor's invulnerability. This significant development marks a key moment in the story, demonstrating that even the most powerful and ancient of evils can be challenged. His key relationships are primarily defined by his position as the ruler of the demon race and the feared enemy of the countless races he has conquered, including humanity. Notably, he also has a transactional relationship with others, such as when he holds a sword spirit sister hostage in exchange for bringing someone before his throne, showing that he uses captives as leverage to achieve his goals. One of his most notable abilities is his sheer presence and authority, which commands absolute obedience and fear from all weaker beings, forcing them to kneel in his presence without question.