Design a photorealistic character of a void arcanist enveloped in swirling mist, captured in a hyper-detailed octane render. Employ Unreal Engine to enhance visual fidelity, incorporating volumetric lighting and HDR effects to accentuate the mystic atmosphere. The character stands tall in a 9:16 aspect ratio, shrouded in shadows, with intricate patterns on their robes that glisten in the ethereal glow, reflecting their mastery over dark, arcane forces. Their eyes shimmer with an enigmatic light, casting an aura of mystery and power.