510 - 16-year-old Nimue's access to Morgaine Le Fay's magic is disrupted by the Phantom Stranger, driving her to study under Merlin.
517 - 23-year-old Nimue participates in he 2nd Shadowpact. unable to access raw magic any longer, she travels from England.
1264 - Nimue serves as a fortune teller in the courts of Kublai Khan, taking the name of his city a Madam Xanadu.
1267 - Madam Xanadu leaves the courts of Kublai Khan.
1606 - Madam Xanadu falls in love with a woman in Spain at the height of the Inquisition.
1610 - Madam Xanadu fails to gift her lover with immortality before she dies at the hands of the Inquisition.
1787 - Madam Xanadu becomes an adviser to Marie Antoinette.
1790 - Madam Xanadu leaves Marie Antoinette's court when she refuses to heed her advice.
1898 - Madam Xanadu, sensing the coming resurgence of Magic, opens her fortune tellers shop in the growing city of New York.
1934 - Madam Xanadu becomes a regular source of information to Jim Corrigan as he tries to understand the Spectre.
1943 - Madam Xanadu is contacted by the Phantom Stranger on behalf of John Sergeant, and helps them summon Kent Nelson & Jim Corrigan. She is unable to join them in forging the 3rd Shadowpact as she had participated in the 2nd, but she assists them.
Character's like Xanadu exist in this neat periphery of DC... they've been around for a very long time, sharing the same universe as Batman and Superman, but never quite feeling like they exist in the same world. There have been so many fascinating stories built using the various magical realms of DC... some of them notably adult in their subject matter. Of course, this later went on to fuel an entirely separate comic imprint: Vertigo grew from the fertile soil of DC's penchant to have robust, dark, sexy stories. Still, Xanadu and other characters like her continue to be part of the fabric of DC.
She's a fantastic character, however you use her... a mysterious seer occupying her magic shop buried in one of the back alleys of New York City, predicting the future with her tarot cards and wielding magics that defy understanding. Her specific story has been told in some absolutely fantastic comics, and we really haven't changed much. As she's one of very few characters to have been active stretching all the way back to the court of Camelot, we absolutely included her in the 2nd Shadowpact, building on her relationship with Morgan Le Fay and Merlin. She continues to serve as a crux for several different stories, always operating in the background.
During the major comic event 'Day of Vengance', Xanadu was blinded, and she went on to always be featured with a blindfold as she told her fortunes. It's a neat visual, but beyond that it doesn't really expand the character in a meaningful way and, in some ways, kind of blunts the innate sense of power that makes her so cool, so we've decided against it.