The story began with Selûne as a youthful and beautiful goddess, residing in a mystic realm populated by deities. Turning aside from a life of ease, she was impulsive and grew tired of life in her own plane. Thus, she "borrowed" a wand of great power from a god known only as "her father" and used the wand to fly away in a bubble of force, so that she might experience life in other realms.
In time, she traveled to a far-away plane with a forbidding blood moon palely glowing over a barren land. There, Selûne was smitten by a mysterious and attractive warrior, a lord of his people. The stranger persuaded her to use the wand to transport him and his followers to Toril, riding upon winged beasts, where they planned to settle. However, once they landed, he revealed his true form and intentions—he was the monstrous Imgig Zu. He and his people were hideous shapechanging monsters, set on conquest and ruin, and now on killing the deceived goddess, which he had the power to do.
Fortunately, help arrived in the form of a brave young wizard riding by on horseback and racing to her rescue. Although the wizard was not powerful enough to defeat the monsters, he was capable of causing enough confusion and chaos that Selûne could escape. The goddess, now freed from her subjugation, used the only thing she had left: her own life force. Draining her life force away, she imprisoned the monsters inside a pocket dimensions within a gigantic moonstone. She reduced the gem, now known as Selûne's Eye, in size and gave it to the young mage who'd rescued her for safe keeping.
However, the price of victory had been great. By using her life force, Selûne had weakened herself and sacrificed her immortal youthful vitality and beauty, aging thousands of years. This was a fact she kept hidden from the young wizard.
The story had a few alternate endings, depending on locale and the point the storyteller wished to make. In some, Selûne learned her lesson and went back to her home, and brought the young mage with her. In others, Selûne died because of her sacrifice, but was resurrected come the next full moon. Still others told that the young mage loved her, but she rejected his advances because she was no longer young or beautiful.
Luna, proprietress of the Selûne's Smile inn in Waterdeep, and in truth an avatar of the goddess Selûne herself, told the tale as a bedtime story for the young kittenlord in the Year of the Prince, 1357 DR. His guardian, Conner, overheard and remarked upon how poignantly she told it.