One thing is certain, though, isn't it? The fairy tale character Bluebeard was based on him.
Absolutely false! This is one of the most persistent and idiotic myths about Gilles de Rais; a moment's thought should be sufficient to debunk it. Why on earth would a supposed murderer of children be transformed into a suave ogre of a wife-killer?
Perrault published his tale in 1692, a quarter of a century after Gilles' death. It was almost two hundred years after the publication of Bluebeard before anybody thought to link the disgraced hero with the murderous husband. Eugène Bossard, Gilles' first biographer, was not a folklorist and was spectacularly ignorant about the genesis of popular stories. He was writing a thesis on French literature; his goal was to link Gilles to the Breton Barbe Bleue legend, and he ignored any evidence that contradicted him, including the more apposite figure of Comorre the Cursed, a local supposed uxoricide. Comorre would have been a far more likely model, had Perrault been looking for one. But he had no need for such a thing: his conte is based on a tradition that is found all over the world. Bluebeard is only one of many demon lovers with a dark secret and a habit of killing wives, including the ancient Mr Fox, mentioned by Shakespeare and still a thrilling tale . As we know, Gilles had one wife, who outlived him.
Further reading -
The B Word
Comorre the Cursed: the original Bluebeard?
But he was wildly extravagant; it must have been a sign of mental imbalance that he spent so much money on a play?
Not by the standards of his day. As a nobleman, he was expected to display his wealth; he may be compared with René d'Anjou, his contemporary and another great sponsor of the arts. His brother may well have complained of Gilles ostentation in his chapel and his love of the performing arts; when the King wrote to his heirs in 1446, restoring some of their inheritance, he mentioned none of these things. He blamed Gilles' financial problems on bad servants, lack of order, poor management of rural smallholdings, and alchemy. He might have added: subsidising and providing an army to assist an impoverished Dauphin.
Further reading -
Holy Innocents
Money matters