The Wandering Unicorn

El unicornio, translated in English as "The Wandering Unicorn" (1965), is a novel by the Argentinian author Manuel Mujica Láinez (1910–1984) in which the legend of Melusine is developed. Set in medieval France and Palestine of the Crusades, Láinez’s novel is a mixture of fantasy and romance which is narrated from the perspective of the shape-changing Melusine.
The events of the original legend of the medieval Romance are recollected early in the novel. Melusine, a fairy, marries Raimondin of Lusignan. However, when he spies her transformed as half-serpent, she flies away with frightful screams. Associated through marriage with the Lusignan family, Melusine appears over the centuries on the towers of their castle, wailing mournfully whenever a disaster or death in the family is imminent.
In Láinez's novel Melusine embarks upon an adventure and unrequited love-affair with Aiol, the son of Ozil, a crusader knight who bequeaths a unicorn's lance to his son. Together the young knight Aiol and Melusine travel across Europe encountering monsters, angels and Knights Templar, before eventually arriving in war-torn Jerusalem of the Crusades era.
Láinez’s novel of magic realism generates empathy towards Melusine as she recollects her adventures, before the love-affair between a mortal and an immortal concludes in a sad and tragic ending.
Editions.
"The Wandering Unicorn" (1965) translated by Mary Fitton, with an introduction by Jorge Luis Borges, Berkley Books, 1985