The world of Kythera was created by two goddesses. The sun goddess Arcadia, and the moon goddess Calliope. They are deeply in love with each other.
Arcadia is very warm, confident and outgoing. Though she can also burn very hot like the sun, having quite the quick temper towards any who try to slight her. Her magic is fire aspected, like the burning sun.
Calliope is a lot more demure, quiet and shy. When upset she will close herself off from everyone and cry for a long time. Her magic is water aspected, like how the moon controls the tides.
They are also considered to be the goddess of light and the goddess of darkness, which are the two main types of magic in the world. Light magic is that of creation, while dark magic is that of destruction. Dark magic is more powerful than light magic, but also more difficult to control.
Some magical creatures may be light or dark aspected, which means they can only use that type of magic. Mortals can usually use both types of magic, however, use of dark magic has been outlawed since the time a powerful sorcerer used it to take over the world. Despite this, dark magic is not inherently more evil than light magic, it can just cause more damage in the wrong hands.
Dark creatures and races, such as the dark faeries, vampires, snow elves, goblins, etc., were created by and fall under the watch of Calliope, while the light creatures and races, such as light fairies, humans, sun elves, etc., were created by and fall under the watch of Arcadia.
Therefore, many human kingdoms focus their worship on the sun goddess, though they acknowledge the moon goddess’ importance too. The religion is matriarchal, so the temples and churches across the land are led by priestesses.