Vikings arrived and began a settlement with help from their Irish thralls. But they weren't alone. All manner of otherworldly beings lurked in the island's hidden corners. The Vikings called these beings vættir; the Gaels called them Aes Sídhe.
Among these beings were the selkies who frolicked at outcroppings on the shore. These creatures looked like seals in the water, but they shed their hides on land to reveal beautiful human forms underneath. The Norse chieftain Valbrand saw the prettiest female selkie, whose name was Eyfridh, and decided he wanted her for himself.
As Eyfridh slept on the beach at the edge of the forest, Valbrand snatched her sealskin and bundled it into a hidden bag. When she awoke, she saw that she couldn't return to the water, and she had no choice but to go home with the powerful chieftain before her.
They got married and had a son, who they named Asgeir. This son grew into a strapping young lad, but he noticed that his mother was never happy. She would sit on a rock at the beach and gaze longingly toward the horizon. Asgeir wondered why she was so forlorn, not realizing that she pined for her old home.
During her captivity, Eyfridh's only friend was a woman named Ginna, who regularly came down from the forest to keep Eyfridh company on the beach. Ginna was another of the island's mystical beings. From the front, she was every bit as lovely as Eyfridh. But when Ginna turned around to return to the woods, Eyfridh saw a furry tail swishing behind her and a back as hollow as a dead tree. Eyfridh decided to ask about this, and Ginna explained that she was a type of vættir called a huldra.
During this conversation, Eyfridh let slip that she herself wasn't human, and that Valbrand had captured her from the sea. Ginna was horrified at this. The next day, while the chieftain was leading a raid on a nearby island, Ginna slipped into his longhouse and observed the exact nook where Valbrand had hidden the sealskin. She reported this to Eyfridh, who vanished that night and was never seen again. The boy Asgeir missed his mother from then on, but he hoped she was somewhere that she could be happier.
Years later, when Asgeir was a man, he ventured through the forest and met Ginna. As a supernatural creature of the wild, the huldra had not aged a day, and she noted that Asgeir looked remarkably similar to her old friend Eyfridh. He explained that that was his mother, and asked if Ginna had any idea where Eyfridh had gone. Ginna explained that Eyfridh was a selkie who Valbrand had kidnapped and who had run away to return to her old home. Asgeir was shocked that his father would do something so cruel, but now he had context for why his mother had always been so sad. He took further comfort in knowing that she was indeed happier now.
Upon returning home, Asgeir realised that he'd taken a liking to the ethereally beautiful being he'd met. But he was concerned about wooing her because he didn't want to wrench her from her home like Valbrand had done to Eyfridh. Asgeir decided to go about courting Ginna more respectfully. He brought lunch to a clearing in the woods and called Ginna over to dine with him. That date went well, so they continued their courtship every day at noon. Eventually, they'd grown comfortable enough with each other that Asgeir invited Ginna to spend the night at the chieftain's longhouse. At supper, it took all of Ginna's self-control not to throttle the ageing chieftain Valbrand for what he'd done to her friend, but she stayed her hand because killing him would give Asgeir and the other mortals too much trouble.
Several years later, Asgeir and Ginna married and had a child of their own together, a daughter named Ingileif who strongly resembled her mother. Ingileif's parents never told her about her supernatural heritage. But Valbrand's thralls who cared for the girl passed down legends of the vættir and Aes Sídhe until the old chieftain died and Asgeir freed all his father's thralls. Eventually, once Ingileif had grown and Asgeir himself was beginning to age, he took his daughter to the shore and introduced her to her grandmother Eyfridh.
"Hello again, Mother," Asgeir called out to the sea. "I have grown now!"
A seal swam to the beach and shed its skin to reveal a human form. Looking on in amazement, Ingileif excitedly cried, "It's a selkie! The stories were true!"
Having never met Ingileif before, Eyfridh initially thought she was looking at her old friend Ginna. "How do you not recognise me?...Wait a minute, you are Ginna the hollow-backed huldra, right?"
Puzzled, Ingileif turned to her father and declared: "This Sídhe is bananas, I ain't no hollow back girl!"
