Gilles then asked a priest named Eustache Blanchet to find him a magician. Several were tried, but the results were poor until one of them, a man named Fontanelle, succeeded in conjuring up twenty crows whereas the others were not even able to conjure up a few birds. But Fontanelle also claimed he had conjured up a demon called Barron; Gilles was then advised that his only way of learning to make gold was to agree to sell his soul to the Devil. Despite his taste for killing children, Gilles remained a devout Catholic; so deciding to invoke the Devil must have seemed a far more frightening step than murder.

But finally, he and his cousin Gilles de Sille locked themselves in the basement of his castle at Tiffauges, together with Fontanelle, and prepared to converse with demons. The magician warned them solemnly not to make the sign of the cross, or their lives would be in great danger. Sille stayed by the window, prepared to jump out; Gilles ventured fearfully into the magic circle and watched the beginning of the conjuration. The legend says that the three men were brutally ejected from the donjon before the roof collapsed. Fontanelle disappeared, either killed or escaped.

However, Gilles needed money so badly that there seemed no other way than continuing with his magical experiments. In 1439, he sent the priest Blanchet to Italy to search for a more skilled magician; Blanchet returned with a "clerk in minor orders" called François Prelati, a young man of great charm--and also, apparently, a homosexual. It is hard to know whether he was simply a confidence trickster or whether he had some genuine knowledge of the magic arts; but Gilles found him immensely attractive and trusted him completely.

Prelati told him that they would have to offer a child's blood and parts of its body as a sacrifice to the Devil; Gilles agreed but still refused to take the final step, of selling his soul to the Devil. Prelati told him that in that case, he would have to continue the conjurations alone. During one of these sessions, Gilles and his cousin heard loud thumps from inside the room; they looked in and found Prelati "so hurt that he could hardly stand up." He explained that he had been beaten by the demon Barron, and had to take to his bed for several days, during which time Gilles nursed him tenderly.

On another occasion, he rushed out to tell Gilles that he had finally conjured up a heap of gold. Gilles rushed back to see it, but Prelati was there first; as he opened the door, he staggered back and shouted that a huge green serpent guarded it. Gilles fled. When he returned, the gold had vanished, leaving only piles of dust...