She leaves the safety of her forest upon learning that she is the last unicorn in the world, with information about the Red Bull as her only clue. When she first encounters the Red Bull, Schmendrick manages to inadvertently change the Unicorn into a human female to confuse the Red Bull and force its withdrawal. Schmendrick calls her "Lady Amalthea" so as not to arouse King Haggard's suspicions. Beagle notes that he took the name "Amalthea" from a Greek deity with the same name. Actually, Amalthea was the goat whose milk was given to the infant Zeus.
The Unicorn's goal is to find the rest of her species, which have been driven away, under Haggard's instruction, by the Red Bull.
The friend that the Unicorn makes is Schmendrick , when he frees her from Mommy Fortuna. He is delighted when she asks him to accompany her on her quest, and does all he can to protect her.
Her other friends are Molly Grue, the Butterfly and Mommy Fortuna's Animals.
The Unicorn becomes good friends with Schmendrick and Molly Grue, but her biggest relationship is with Prince Lir. At first, she ignored his advances but when she begins to forget her identity, she softens towards him, and when Lir expresses his love for her, she falls in love with him as well. Later, when her true identity is revealed to Lir, his love for her remains, which prompts her to stay human and abandon her quest. Lir, however, disapproves, and believes the quest can't be left. The Red Bull appears, and Lir tries to defend her, while she is turned back into a unicorn in the process. When the bull kills him, the unicorn forces the bull into the sea and the other unicorns run free. On the beach, she revives Lir and leaves for her home. Schmendrick tells Lir that the unicorn will love him for the rest of time.
Many people try to catch The Unicorn, each for their own purposes, and these are her enemies. Among these people are:
- King Haggard
- The Red Bull
- Mommy Fortuna
- Captain Cully