Demon King

Few details of the Demon King's looks survive. The ruler is said to have worn a full suit of plate armor, and like so many of demonkind, bore a pair of horns.

Where most demons prize their own individuality, the Demon King did the opposite, instilling order across demonkind and commanding its lasting loyalty. He shared with Macht a stated wish for humans and demons to live side by side, but his method was monstrous: he slaughtered people in great numbers to grasp how they thought, ultimately shrinking humanity's domain by a third. Solitär observed that he, Schlacht, and Macht all displayed traits unusual for their race, even as none could escape the fundamental nature of a demon. That hunger to understand mankind drove deep research, which extended into the study of living things in general; from it he formed a notion of convergent evolution to account for the gap between land mammals and creatures of the sea, an idea he later passed to Solitär.

By Heiter's account, the Demon King had ruled demonkind across more than a millennium by the time the Hero Party set out, from the moment demons first surfaced in human history and the fighting began. Roughly a millennium before Himmel's day, he ordered the elves wiped out; the assault on Frieren's home, led by Basalt the Throne, left her the lone survivor. That tragedy steered her toward Flamme, the mage who trained her and charged her with someday ending the Demon King, a charge she would honor centuries on.

Not long before Himmel sought Frieren out, the Hero of the South opened a year-long offensive that broke the army's front line, prompting the Demon King to send Schlacht the Omniscient to remove him. Schlacht rallied the entire roster of Sages for the task, and the clash claimed his life, three of the Sages, and the southern hero alike. Some seven years later, the Demon King set demons to guard the Goddess's Monument, convinced a visitor from nearly a hundred years ahead would emerge there. Three years after that, the Hero Party of Eisen, Frieren, Heiter, and Himmel finally breached the Demon King's Castle and struck the ancient ruler down. His power was immense, befitting a being every other demon obeyed and one whose mana, by the logic of demon hierarchy, towered over all others; Serie credited him with extraordinary sensitivity, for he alone saw through Frieren's suppressed mana the instant they met. Frieren has said the party could never have prevailed had a single member been absent.