Why do people call Mary Magdalene the "Black Madonna"? Today I heard something most peculiar, and was wondering if there is a Biblical basis and/or if there were other denominations that teach this.

An older gentleman whom I know very well, and almost think of as a father, during a discussion about Mary Magdalene said (verbatim):


  Oh, well you see - some call her the "Black Madonna." (Because we had talked about theories as to whether her and Jesus could have been married - though this is irrelevant to the question at hand)


This is a most perplexing "revelation" to me, knowing that Biblically we know that Mary was saved from a life of sin to serve Jesus Christ.

I've looked all over the internet, and the most I can find about anything "Black Madonna" related is depictions of Mary, Mother of Jesus as a black woman.

What is the basis for this teaching? Is there any Biblical basis it? What groups teach it today?
Mary Magdalene is known as the "Black Madonna" and conflated with a fertility goddess (Isis, the Black Goddess) in Gnostic thought, popular among Templars and Cathars back in the day and with more written about it in the Gnostic Gospels found more recently at Nag Hammadi. You can read an article about the Gnostic cult of Mary Magdalene here.