What do you call a fairy tale animal with a single horn?

Unicorn

On which sea would you find the port city of Odessa? What chemical element makes up about 78% of Earth's atmosphere? Who developed the assembly-line method which revolutionized American manufacturing? What is the name of the event in the 1830s when tension among settlers wanting silver and gold land claims led to forced relocation of Cherokee peoples? Which document during the 1820s warned Europe not to colonize further in the Americas, pledging U.S. neutrality?