Gwen ferch Ellis was born at Llandyrnog in the Vale of Clwyd, but was sent as a young girl to live with an uncle at Yale near Wrexham.
In the year of the Spanish Armada, 1588, Gwen and her second husband, a miller, went to live at Llanelian mill near Old Colwyn. But he died and she married yet again, this time to a Betws-yn-Rhos man.
She was a weaver, but she also had a special gift - she could heal animals with home-made potions described as 'plasters and salves'. She was a female equivalent of the dynion hysbys of Wales, a colourful line of healers who also practised minor magic such as 'discovering' lost items.
Gwen was paid in kind - mainly with food and wool - for her services; she used incantations to 'heal' animals and the superstitious folk around her. Many travelled long distances to seek her advice.
Her magic formula was to recite an incantation, one of which started with the words: 'In the name of the Father, the Son and the Holy Ghost...' She would attempt to protect people from illness, or natural disasters, or from evil, especially malicious neighbours who could take on the imagined form of rapacious night-wolves.
But Gwen made a fatal mistake - she tangled with the rich and famous, poking her nose into the private business of a major landowner.
One of her incantations, written backwards and therefore deemed very dangerous, was discovered at Gloddaeth Hall (now St David's College), near Llandudno.
This was the home of Thomas Mostyn, justice of the peace and a major power in the land.
Unfortunately for Gwen, she'd become involved with a certain Jane Conway from Marl. Jane was a rather shadowy figure who claimed that Lord Mostyn had failed to pay her for services rendered.
To make matters worse, Gwen ferch Ellis confessed to spending a night at Gloddaeth when the lord and master was away from home.
This was a bad move and she was thrown into Flint Jail in 1594, when she was about 42; there she was questioned by the Bishop of St Asaph.
Later that year a formal investigation was conducted at Diserth Church at Llansanffraid Glan Conwy, at which five witnesses - five men and two women - gave evidence against her.
For instance, Elin ferch (the daughter of) Richard from Llanelidan claimed that her son had gone mad after Gwen had struck him during a row.
Gwen ferch Ellis appeared before Denbighshire Court of Sessions in the autumn accused of killing a man through witchcraft; of grievously harming another man by breaking his arm, and of grievously harming a woman by causing her limbs to become useless.
No mercy was shown to her and she was duly hanged.
Though there had been other court cases before hers dealing with magic or sorcery, Gwen's was the first case arising from an accusation of black magic or maleficium.
But it wasn't the last. For instance, in 1623 a Rhydderch ap Evan and his two sisters, Lowri and Agnes, from Llanbedrog, were found guilty of using sorcery to kill Margaret Hughes from the same village, and of laming Margaret's sister Mary and causing her to become deaf.
Witchcraft and sorcery were social obsessions during that period. This is illustrated by the fact that Jane Conway from Marl was the mother of two experts on the subject - Robert and Henry Holland, both of them Cambridge graduates and church ministers in England. They both wrote pamphlets on witchcraft.
A fuller version of this story, entitled Y Ddewines o Gymraes Gyntaf i'w Dienyddio: Achos Gwen Ferch Ellis, 1594, by Richard Suggett, can be found in Cof Cenedl XIX, edited by Geraint H Jenkins (Gomer).
