The Lady of the Lake is best known through the Arthurian legend. 
Two of her most common names are Nimue and Vivienne, and she has strong ties to Morgan Le Fey. 
 
According to Arthurian legend, she was the foster mother to Sir Lancelot. It is told that Merlin was in love with her and taught her all of his powers. She became his student, his scribe, and his lover. 
She recorded his prophecies and she became more powerful than him. She imprisoned Merlin inside of a glass tower, either to protect him or to bind him – no one knows for sure. Whatever the reason, she did love him. And she was among the queens who escorted Merlin’s beloved King Arthur to Avalon as he was mortally wounded and lay dying.

Oil pastel by Gwendolyn LaFae 

In Celtic Society the Lady of the Lake was extremely popular for her influence over the essence of life itself. They celebrated the beauty of the lakes and springs. The way the water danced and flowed was a sign of the Goddess and her supernatural powers. It was common for them to throw offerings into the waters, such as valuables and weapons. Imagine seeing Excalibur, the powerful sword which belonged to the Lady of the Lake , slowly descend down into the waters by her hand.  This practice of giving offerings to the Lady of the Lake continues today in the form of “wishing wells.” 
Nowadays, The Lady of the Lake is remembered as “Lady Luck.”

Pray Peace

Personal note:
I have wanted to do a project on The Lady of the Lake since I began Goddess lessons.  I have had a fascination with the Arthurian legend since I was a child. I have read numerous books and papers, seen most of the movies made, and I wrote my college term paper on this legend. The male characters remain consistent in each version of the story, however when trying to focus on the females, I noticed the story lines for the female characters are not consistent. Her names, her roles, her actions and motives, they all change with each version of the legend.
So what does this tell me? We as Goddess are not easily defined. We are versatile and hard to categorize.
We are capable of fulfilling any role, and all roles. To me, The Lady of the Lake is the essential presence in an incredible legend focused on male characters. Without her they would not have a story, and without her versatility, they would not have a great story.