Where can I find battle chess?

Stalemated trying to find fantasy chess story

• I'm trying to track down a fantasy short story based around a real life infamous chess game. Years ago I read a short story in a collection that I borrowed from a library. Details are a little hazy but it was fantasy, was set in some sort of inn and was based around a chess game between a man and some sort of intelligent talking unicorn (I think - it could have been some other fantasy creature) that may have also have had psychic/magic powers. I'm not certain but I think it was by Robert Silverberg. I can remember reading in an introduction to the story that the writer had three requests for short stories for fantasy collections themed around 'inns', 'unicorns' and 'chess games'... so he wrote one that combined all the elements and sold it to all three. The introduction also said that the moves of the game in the story were taken from an infamous real life chess that involved, I think, cheating, or accusations of cheating or some other notoriety, that the author had taken from some book. Googling's failed me so if anyone has any idea what the story, and/or the real life chess game itself might be, I'd be grateful.

• Answer:

  Could it be a story from http://www.amazon.com/exec/obidos/ASIN/0441654827/metafilter-20/ref=nosim/ edited by Fred and Joan Saberhagen - maybe the story "Unicorn Variation"? (I haven't read it - this is just from Googling - sorry if it's way off.)