Dance of the Changing Serpent?



Does anyone remember what/where this little spell/ritual comes from? I remember it had something to do with the Picts but that's about it. I don't think it was part of REH's original stories, but i can't figure out which pastiche it could have come from.
you wouldn't happen to remember what it does would you? :?:

Or for that matter, where i could find that story :D
Yeah, it was in Wolves beyond the Border, which I read the draft of in The Conan Chronicals Volume 2: The Hour of the Dragon, put out by Gollancz Publishing in Great Britain. The Pict shaman puts the spirit of a man in a Ghost Snake and the Ghost Snakes spirit into the man. After a minute of watching the snake try to walk and the man try to slither he cuts off both their heads. The Picts seemed to think it was good for a larf.