Elite merfolk guardians before a vast underwater city

A group of elite merfolk guards standing watch outside a majestic underwater city. The merfolk have powerful, athletic builds with shimmering scaled tails in shades of emerald, sapphire, and pearl. They wear ornate coral-and-bronze armor engraved with ancient ocean runes and carry tridents, spears, and enchanted shields that glow faintly with blue magic. Behind them rises an immense underwater city of spiraled coral towers, shell-domed buildings, glowing sea-crystal windows, and bioluminescent plants lighting the streets. Schools of fish swim through archways, and rays of sunlight filter down through clear ocean water, creating dramatic god-rays. The scene feels noble, ancient, and vigilant. High-fantasy Dungeons & Dragons art style, ultra-detailed, cinematic composition, epic scale, realistic anatomy, painterly illustration, vibrant colors, dramatic lighting, no modern elements, ultra high resolution, 8K quality.