Unicorns are a fictional species seen in the Harry Potter series.
Unicorn foals are silver or golden (possibly depending on gender) and remain so until their horn grows, at around four years old. At seven years old, they are fully grown and their robe is a blindingly pure white, though their hooves remain golden their whole life long. Unicorns are too fast for any normal creature (even a werewolf) to catch them, as it takes magic to do so. However, some desperate wizards are sometimes willing to slay a unicorn using magic, as drinking their blood is a way to escape immediate death by illness or injury, although it carries a curse that condemns whoever drinks it to a 'half-life'.