For Witches Fate was one of the six creative concepts that Aine created to guide her creation using ideas she believed they would need to survive. After, the concept of magic, Ceri, created Dragons it became clear not only could they guide they could create races. Nature realizing that he could not be everywhere but that there were many places like woods that would need to be safeguarded and other things related to nature like seasons and animals created the first fae who created more of his kind and they were charged with this task. It was this act and the idea of balance that lead fate to create a being to look after the waterways of their world.
He realized that water was needed for life and with all the oceans, streams, and other such things they would need protected also so he would make them a protector as well. He went to the center of the sea and placed one of his own tears into the water using his powers the waters swirled around it as he bent those waters to his will As the first Fae was a man he decided the first f his creations would be a woman. I time he would marry the two of them together and thus ensure the two protectors were united.
The water took shape by the will of his mind and slowly from it took the form of a brown hair female with a dress made of crystal water that clung to her. However, unlike nature that created the first fae, Irial and left him to find his path. He decided he would ensure that his creation was put on the path he chooses. He was Fate after all.
So, he named her Sereia and told her he would see her grow as strong as the ocean itself. She only wanted to play with the water and exp, or this new world but her father was a taskmaster and demanding. He always pushed her and she annoyed him rebelling at every turn even refusing to marry the fae king. she swore she would give no other man power over her and made all mermaids female. After her father's death she learned he was right she had to be strong to protect the sea and thus the powerful mermaid queen she is today was born.