A unicorn is a privately held start-up business worth over a billion. They are quite rare.
The English word “unicorn” refers to a horse with one horn and is often associated with various activities involving non-Jewish mysticism and witchcraft., so Jews should probably stay clear of them. Given the level of natural science in the middle ages, it is possible rabbanim identified them incorrectly with the tachash.
If one mutilates a horned animal, e.g. a goat, one can create a creature with one horn. Halacha prohibits us from doing so.