Okay but consider this: mermaids in space
Space mermaids? As in: alien mermaids that live in the vacuum of space and swim between the stars? A setting that uses the analogy of deep space as the open ocean but keeps all the sea monsters? DO WANT!!
Luring astronauts into black holes with a song that carries across the void where no one can hear you scream
Not audible song, though—maybe they sing in frequencies that ship’s sensors pick up—as distress beacons, as spaceports, as fleets. They would have to be huge, to travel between stars, massive space-black bodes with biolumescent patterns, photosynthesizing pure starlight into fuel, too enormous and frail to hold up in the atmosphere of a world. Fins that catch solar radiation instead of water, schools of them slingshotting between stars. Eggs laid in the tails of comets that warm and hatch as they rocket around suns. Voices that are heard in the slow radio pulses of quasars; language of half-light. Homes in the shelters of nebulae, like clownfish and sea anemone. They gather together star-stuff, shape solar systems like we build houses. Maybe, like certain breeds of lobsters, they never stop growing, so there are a few really ancient ones, star-eaters, curled up and sleeping in the warm glow of red suns, layered over with a crust of asteroids; so big passing ships assume they are young worlds, the slow thrum of their heartbeats like the pulsing of a binary system. Mermaids so large a fleet of ships is little more than krill; the universe is vast, and they live in the darkness between tiny islands of light.