The witch option is based on reality in so much as what these 'witches' or sorcerers did (and still do in some places) is take herbal, natural medicines, cures, etc. with folk knowledge and a lot of smoke and mirrors and give it to their clients.
I've been reading Tuchman's A Distant Mirror on the history of the 14th Century and while things of that latter period are moving towards the renaissance I don't think we should underestimate or downplay the effect that simple faith and superstition had on people of this age. Witches, demons, sorcerers, aphrodisiacs, curses and hexes, astrology and other 'pseudo-sciences' were often accepted as 'science' in this age w/c didn't know might better (and in some cases would lead to scientific discovery as in the case of alchemy's contribution to chemistry).
Best regards,
Richmond