The Fable of the Lunar Gem

Once upon a time, on a serene sapphire island untouched by the crutches of humankind, there existed an ancient civilization that was primarily composed of two entities: men and vespertilio-humanoids, or what they liked to call themselves, the 'Nycteris.'
The Nycteris were an intriguing species, with the bodies of humans and wings of bats. They had a unique set of abilities, including echolocation and a lifelong symbiotic relationship with the moon. It wasn't a dreadful existence after all, a providence bestowed with peace and prosperity.
Within this civilization, lived a young lad named Sigmund who was a simple merchant trading mundane earthly items, intrigued by the mystic life of the Nycteris. Their moonlit dances under the serene night sky, their songs echoing in the valleys, everything about them mesmerized him.
On one of his ventures deep into the island, Sigmund discovered a sacrosanct Nycteris child wounded and unable to fly. Against the prevailing norms and taboos, Sigmund decided to help the creature. He named it Solstice and took it upon himself to heal the little one and protect it from the perils that might befall.
Meanwhile, an increasingly hungry fear started haunting the island folks. Elders preached about an ancient prophecy which foretold about their moon, the Nycteris life source, destined to diminish and eventually disappear, plunging their world into eternal darkness.
As Solstice grew under Sigmund's care, an unusual friendship blossomed between them. Every day, Solstice would perch on Sigmund's shoulder and venture along, helping him in his trades, creating an other-worldly aura with its inherent moon-magic. Slowly, Sigmund's business thrived, and he became a prominent figure in the island market.
As the prophecy started taking its dreadful form, the moon began to wane unnaturally. The nights grew darker, and the Nycteris's powers began to weaken. Stricken with fear, they concluded that the prophecy was a punishment for an impure action. When they discovered Solstice in the lap of the human realm, they blamed Sigmund for their impending doom.
Wrongly accused and exiled from the island, Sigmund sought refuge in a remote cave with Solstice. While despair was drowning them, Solstice revealed a hidden truth. It whispered about an ancient Lunar Gem that held the power to restore the moon's light and thus, could save their world from the looming darkness. Not wasting a moment, Sigmund embarked on a perilous journey to reclaim the moon.
Bearing countless hardships, crossing treacherous terrains, and outsmarting lurking predators, they discovered the Lunar Gem in an abandoned shrine. There, Sigmund fought with all his might against the shrine’s guardian - a venomous Chimera. With Solstice's aid, he subdued the beast and secured the gem.
The duo rushed back to the island, wielding the gem high under the darkness of the night. As soon as the gem came in contact with the waning moon, a stunning spectacle unfurled. A radiant beam shot up from the gem, igniting the sky and returning the moon to its former luminosity.
In awe and gratitude, the Nycteris welcomed Sigmund back, apologized for their ignorance, and recognized the unity and friendship that had saved them. Through this ordeal, the Nycteris and humans realized the value of interspecies empathy, cooperation, and coexistence. And so, they pledged to live harmoniously, cherishing their interdependence and celebrating their diversity, led by a new hero and his loyal Nycteris friend, thus marking a new chapter in their rich folklore.