zombie soldier, Call of Duty, Der Riese map, declassified easter egg, step-by-step guide, hidden messages, secret rooms, vintage military uniform, glowing eyes, undead, horror atmosphere, abandoned factory, industrial structures, rusted pipes, flickering lights, eerie shadows, moonlit night, intense action pose, holding a ray gun, mid-reload animation, dynamic angle, high contrast lighting, detailed textures, steel catwalks, vintage propaganda posters, mysterious aura, foggy environment, 3/4 view, cinematic composition.