two players, cooperative gameplay, Der Eisendrache Easter Egg, Call of Duty: Black Ops III, zombies mode, ancient castle, snowy weather, medieval armor, intricate puzzles, hidden quests, Pack-a-Punch machine, gravity spikes, elemental bows, boss fight, Keeper Protector, dramatic lighting, moonlit night, dynamic shadows, action poses, teamwork, intense expressions, high contrast, detailed textures, 3/4 view, atmospheric effects, cinematic angle.