Born in a forest, the Unicorn lived a lonely life until a butterfly told her a tale of the other unicorns, and how they were driven into the sea. Deciding that it was her place as the last unicorn to rescue them, the Unicorn undertook a quest to find where they were and free them.
Along the way, she met a magician and a camp cook, both of whom joined her on her quest.
When they reached the forest outside the castle of King Haggard, they encountered the Red Bull that had driven all the other unicorns into the sea. In an attempt to save her, the magician turned the Unicorn into a human girl, but was unable to turn her back.
They sought employment in the castle of the King, the magician taking on the role of court jester, the camp cook in the kitchen, and the Unicorn herself simply taking the rol of Lady. The Unicorn was courted by the King's son, and soon fell in love with him. This nearly caused her to abandon her quest, though when the Prince tried to save her from the bull during the final confrontation and was killed in the process, grief overcame the Unicorn, and she drove the bull into the sea, freeing the unicorns.
Given her time as a mortal human, the Unicorn is changed. No longer like her peers, and no longer human, she is the only unicorn to know what it is to regret, and to love.