The Sun and The Moon

Prologue

Long, long ago
When the world was new, and ruled by none other than Sol and Luna, sisters of the Sun and the Moon,
There was peace. Tranquility. Balance.
The two sisters were inseparable.
Sol, the Princess of the Sun, was the elder. She was known by all.
Her long, blond hair and gentle blue eyes, like the sky, made her beautiful, and her beauty was matched only by her kind, and gentle personality.
Luna, the younger and quieter Princess of the Moon was also beautiful beyond conpare. Long, black hair and silver eyes that shone like diamonds. She never made a sound. Even so, she was known to be just and fair, and loved to play jokes with the children.

The two sisters were beloved and worshipped, bringing the Sun and Moon around the sky, and each received a festival.
For Sol, this Festival was known as The Summer Celebration, the first day of Summer, a time when the sun stayed in the sky. The people danced and sang in her glory as Luna shunned herself to the darkness of the castle, in tradition and honor of her sister.
For Luna, this Festival was The Winter Celebration, first day of Winter last only 8 hours, and then the moon was raised, and stayed in the sky for a week without fault. The people danced and sang just as well, to make up for the nights they slept. In this way, both sisters received due respect, and both were happy.

One day, a strange figure appeared.
She said he came in peace, and met with Sol. She admired her beauty, and envied the elder sister. She plotted to kill her, and take over the land. However, when it came time to lower the sun to make way for the moon and stars, the stranger saw Luna. Fair, silent, and beautiful. She saw her and instantly, she envied her. She cast a spell on the younger sister, and turned a once great ruler into a tyrant. A woman of evil, bringing nightmares and terror each night. When Sol heard of this, she begged a lone sorcerer for a spell to save her sister. "Aye, I can give ye a spell, but it has a high cost." He said, and she agreed. She took him to the castle, and helped him prepare the spell. Luna entered the room, furious, and was trapped in a magic circle. He preformed the spell, but as cost, she was forever banished in the moon.
Sol wept for her sister, and refused to raise the sun. When she slept, her sister met her in a dream. She told her of her prison, the coldness and lack of air. She told her to raise the sun, so that she might at least watch her people grow. Sol agreed, but on one condition: She ask the sorcerer to imprison her, as well, so that she might forever be with her sister. Luna agreed, and Sol went immediately to the sorcerer. She begged him to trap her as well, and he denied her. After some comvincing, he told her "Princess, I cannot promise you that this will do what you desire." 
"I care not! I want only to see my sister!" She demanded, and he agreed. He cast the spell, but it was not the moon she was imprisoned in, but rather the sun. The people wept, for now both their beloved princesses were gone, and they would never meet again. They asked the sorcerer for one final spell, to allow the two sisters to meet. He agreed, saying that he could set up a system where every 100 years, the moon would overlap the sun, and they could meet for 1 hour. The people agreed, and he took the magic that world held, and cast the spell. Sure enough, the moon rose to the meet the sun, and the world was covered in darkness. The people went to the sorcerer, but found him dead. He had exhausted his form, and could no longer preform tricks for the people.
Now, the two sisters watch us, and protect us.
However, should one of the princesses escape, so shall the other. And the Moon Princess will return as that cruel creature, and swallow our world in darkness, and destruction.