I've come across that one before, but in Joseph Jacob's <i>Celtic Fairy Tales</i>. Its clearly got a lot of witchcraft involved in it! Didn't covens have thirteen members, though? Or would the thirteenth member be "the devil" (or Robin, or whichever name you prefer!) himself? The horns are lunar references, I'm sure - twelve months and all that. The Moon tonight was particularly horned, although its never in the sky for that long when its so slim. The spirit of the well was interesting, I'm tempted to just jump in shouting "Bride!" but there's not really much revealed of her nature, so its hard to say for sure. Probably safe to say Bride though, given her significance to Holy Wells. Sorry, I know I should be calling her Brigid - I've Scottish habits!