The Lay of Aotrou and Itroun

In Britain's land beyond the seas
The wind blows ever through the trees

in Britain's land beyond the waves
are stony shores and stony caves.

So begins The Lay of Aotrou and Itroun, an early but seminal work that grew, along with the two "Corrigan" poems presented alongside it in this volume, from a comparatively short but intense period in Tolkien's life when he was deeply engaged with Celtic, and particularly Breton, myth and legend.
Aotrou and Itroun are a Breton lord and lady residing "in Britain's land beyond the seas" during the mythic age of chivalry. Childless and desperate for an heir, Aotrou seeks out a magic potion from a corrigan, or malevolent fairy. When the potion succeeds, the corrigan returns to demand her fee, and Aotrou is forced to choose between his marriage and his life.
Originally written in 1930 and long out of print, The Lay of Aotrou and Itroun may be set alongside Tolkien's The Legend of Sigurd and Gudr n, The Fall of Arthur, and The Story of Kullervo. Like these other retellings of myths and legends, it was a powerful influence on Tolkien's own legendarium.