Qual

Even among demons Qual cuts a monstrous figure, far larger than most of his kind. A blocky jaw, narrow eyes that look stitched shut, and ever-bared jagged teeth dominate his face, which is ringed with pale, mask-like patterning that deepens into his hairline. His ashen-brown skin is wrapped in dark tattooed bands and studded with staples running down his arms and torso, and two tattered yellow horns jut from his head. Light blonde hair sprouts from between those horns and trails to mid-back, while a beard hangs well below his waist. He drapes himself in a fur shoulder cape and wrist cuffs over a long dark-gray loincloth fastened by a chain and a row of tusks, and his fingers end in lengthy red-tipped claws. Sealed in a crouch, he loomed so large that Frieren stood no higher than his knee.

Like all demons, Qual knows nothing of empathy or human feeling, yet he carries himself with an even, unhurried calm. Freed from his seal, he shows no rage and instead hails Frieren as though greeting a long-lost peer, and on learning his master has fallen he resolves at once to avenge the Demon King. He places deep faith in his own magic, caught off guard when Frieren and Fern shrug off his signature spell, but his keen, adaptive mind lets him read the workings of their defense and devise a counter almost immediately.

Dubbed the Elder Sage of Corruption, Qual sowed ruin across the Größe Forest during the Demon King's rule, slaying close to forty percent of the region's adventurers and seventy percent of its mages. The root of his terror was his own creation, Zoltraak, history's first piercing spell, which tore through every defense and protective charm humans then possessed and struck directly at the body. When the Hero Party came to end the Demon King, Qual proved more than they could handle, and Frieren resorted to sealing him away to deal with him later.

Over the following decades, mages across the continent, Frieren foremost among them, dissected Zoltraak and built defenses against it, and the spell together with that new shield became the foundation of modern human magic, demoting his once-unstoppable weapon to a basic technique. His prison held for eighty years, with Himmel stopping by annually to confirm it. Twenty-seven years after the hero's death, Frieren unseals him during a visit to a Größe Forest village; realizing the Demon King is gone, he turns on her and Fern, only to find his killing magic helpless against the very defenses his work had inspired. A barrage from multiple angles fares no better, and Frieren ends him with a single cast of the spell he himself invented.