The Hyakki Gokai is a hyper-stylized, ornate weapon resembling a traditional Japanese demon mask fused with a massive, curved blade. The mask features intricate, asymmetrical engravings of snarling oni faces, with glowing red eyes that emit a faint, pulsating light. The blade itself is sleek and angular, with a polished metallic finish that transitions from a dark, almost black base near the hilt to a vibrant, blood-red edge, giving the impression of a weapon imbued with supernatural energy.