Since the beginning of mankind, the moon watched over the curious humans, and aided them with light, so they weren't restrained by the dark. The humans thanked the moon profusely, and a group of them even started to pray to the moon.
The moon, being the benevolent gentle entity, was touched by these priestesses' efforts and granted them special powers to harness its energy to help the humans, and the priestesses did so wonderfully for years, and they were revered for their services..
The priestesses became healers, aiding the humans with every aspect of life, and everything was going peacefully, but as we all are well aware of, the peace is a fickle thing. Their joy and reverence wasn't to last much.
One day humans started to arrive from distant places with foreign ideologies and morals. The priestesses and the humans welcomed them, and the moon smiled at them seeing how far the tiny humans had come.
The foreigners however had a different idea about God, and thought these humans to be terribly naïve and backwards. The foreigners also were enamored by the riches these humans had accumulated, and wanted it all for themselves.
They were in a dilemma though, about how to conquer those riches without any fight because if they just went and took it, the moon priestesses would defend the humans. They didn't believe in the powers of the moon but they did acknowledge that the priestesses were a force to be reckoned with.
They were also loved by the humans so if the foreigners directly attacked the priestesses, the humans would never submit to them, and they could lose their riches which was unacceptable to them.
They finally came up with the idea as old as time, divide and rule and used a twisted version of their religion to spread lies. They preached that the priestesses were devil's whores, there to corrupt and collect human souls.
They turned their altars into places of their Gods and slowly poisoned the naïve humans against the priestesses and called them witches. They pumped so much fear into the people that suddenly the witches were the enemy, a thing of their nightmares.
They hunted the witches who had once helped save them and their loved ones. They didn't even spare innocent human women, they massacred everyone who was even thought of as a witch.
The witches were tired and angry, and when they started to fight back, well that's what the foreigners wanted from the start, a reason to spread more hate against them. The witches were cast as villains in the narrative and anyone who killed them brutally was cast as a hero. The stories and narratives were so distorted that everyone believed them to be the villains.
The moon was horrified to see what happened to his beloved priestesses, and how vile his lovely humans had turned. He was enraged by the burnt corpses of his priestesses, and for the first time the calm moon wasn't calm anymore.
He turned red and gathered his priestesses and gave them immense power to cast one curse, to protect themselves against these heroes, but the witches had another plan. They had accepted their role as the villain of the story, and if they were going to be the villain, well then they would make the heroes regret even pursuing their shadows.
All the bright witches of the time gathered in a circle, and poured all their pain and anger in the spell. The air even turned terrifying, getting a taste of their wrath. Pouring their souls in, they made sure the curse was strong and unbreakable as it can be.
With that night they took away every hero's happy ending, and cursed them with a bloody fate. They were cursed to be born again and again, and live the most twisted versions of their miserable stories until the time came for their happy ending, which would always stay in sight but out of reach.
All of them gave their lives with the spell locking it, so even the moon who thought this punishment to be a little too much couldn't interfere. The curse was sealed as their tormented souls finally left their bodies for eternal rest and started the endless cycles of tormented lives for these precious heroes.
The world knew these stories as fairy tales, the heroes thinking the books hold so many lies with their happy endings not knowing they were theirs once, stuck in a loop to repent their sins.