A mystical, alchemistic backdrop for an indoor hardstyle festival poster. The scene features a dark, steampunk setting with intricate gears, ancient books, and alchemical symbols merged into the walls glowing softly. The atmosphere is filled with swirling smoke and ethereal purple lighting that casts a magical glow across the scene. The overall aesthetic is a blend of vintage and futuristic elements, combining steampunk details with a mysterious, enchanting ambiance.  --ar 4:5