Well that last is a very good question! They did, in the end, burn Jeanne d'Arc as a heretic, but for a long time the church accepted her voices as a direct revelation of the divine. I'm not sure I have an opinion on Nimue and Morgan, or any of the other 'magical' elements of the Arthurian novels. I didn't want those books to include any sorcery, but it crept in regardless and I let it lie without too much exploration on my part (it kind of goes with that territory). Now as for Nick, I suspect he was hearing his own conscience, but I deliberately do not say that, because he believes he's hearing a saint, and there were plenty of instances where folk did hear or see, or believed they heard or saw, saints, angels or other divine figures. I certainly don't think that's evidence of mental illness (though of course it would be if taken to extremes), but rather as a direct consequence of intense belief during an age of faith, when there really is no easy alternative to faith (as there is now). Those people believed. I might think their beliefs were risible, but I live in an age when there are scientific and technical answers to many of the great questions, and they did not have that advantage, and they lived in an environment which encouraged them to seek spiritual signs. This was a church that could translate a three day old boy into a saint and even, in Flanders, a dog. The church, of course, kept a tight rein on such manifestations and anyone who declared visions, or claimed to have a direct-dial line to heaven, had better be strictly orthodox or else they were going to be burned, and in the end, of course, the church had the power to declare what was orthodox and what was heretical. Jeanne d'Arc, when she failed, was very quickly moved from one category to the other.