The Horn.

Nature This Guardian piece about the appeal of unicorns somehow manages to reach the end without mentioning Blade Runner in how the beast has become central to modern mythologies. That what could be an artificial lifeform, the arguable pinnacle of human scientific and technological achievement could dream of something that exists purely in fantasy and magic is an extremely potent concept:

"“The unicorn has been popular at various points for at least 3,000 years,” says Dr Miles Leeson, director of the Iris Murdoch Research Centre and a lecturer in English literature. “They were considered as real in the ancient world by the Greeks – they appear in books of natural history, not books about the gods. The Old Testament contains possible mentions of unicorns, and from there they have been incorporated into Western art and culture, surfacing at various times, including the Medieval period and the Renaissance. The unicorn also has a role to play in Chinese mythology.”"

I've always thought the unicorn's appeal is that it feels like it could have existed. As the piece reminds us, the narwhal, a creature with just such a horn does exist, albeit in dwindling numbers, so it's not unimaginable that at some point there was a breed of horse with a similar piece of headgear but later became exist. At least it makes better sense than a pegasus. A horse with wings is just silly.