The Nightmare's Eye is a semi-realistic, ornate artifact resembling a large, pulsating eyeball with a dark, violet iris that glows faintly, surrounded by intricate Norse runes carved into its metallic casing. The surface is smooth yet slightly weathered, with veins of glowing energy coursing through it, giving it an eerie, otherworldly presence. The casing is made of a dark, aged bronze with subtle engravings depicting scenes of ancient nightmares, adding to its mystical and foreboding aura.