She was born to rule an empire that her own family had spent two centuries shrinking with every marriage bed they shared. Mariana of Austria arrived in the world on Christmas Eve 1634, the second child of the Holy Roman Emperor and a Spanish infanta, which made her the niece of the man then sitting on the Spanish throne. Her parents were first cousins. Both halves of her family had been marrying each other for over a century, and nobody in Vienna or Madrid saw a problem with it.

Keeping the blood inside the family was the whole idea. The family paid for it in dead children. Only about half the babies born into the Spanish Habsburg line lived to see a first birthday, while out in the villages four in five infants survived their first year. Mariana herself carried one of the highest inbreeding coefficients of any Habsburg queen, and she would bury three of her five children.

The jaw that she passed on—the famous Habsburg lower jaw that grew out past the upper one generation after generation—would reach its worst form in her son. When she was eleven, Mariana was formally promised to her first cousin, Balthazar Charles, the prince of Asturias and the only legitimate son of King Philip IV of Spain. The boy was sixteen, good-looking, energetic, and heir to the largest empire in the world. That October, he went with his father to Zaragoza and fell ill with smallpox.

He died on the 9th of October 1646. Philip IV, a widower of two years with no son at all, was suddenly left with a problem and a solution sitting right next to each other. Rather than lose the Austrian alliance that the marriage had been meant to secure, he took his niece for himself. The girl who had been engaged to his boy would now marry the father.

The wedding took place on the 7th of October 1649, in the parish church of a small village fifteen miles outside Madrid. She was fourteen years and nine months old. He was forty-four. The new queen arrived in Madrid a lively girl with red cheeks and dark eyes, full of energy, and carrying what one writer called an insatiable ambition to enjoy life and make the most of it.

Along the road, when the king’s dwarfs were brought in to entertain her, she screamed with laughter, and the mistress of the robes took her aside to reproach her. A queen of Spain did not laugh out loud at buffoons. A queen of Spain did not walk in public either, or show her feet, or do a great many other things. Mariana made light of this prudery.

She had no idea yet that the countess was describing the rest of her life. She learned quickly. The Alcazar of Madrid was a dark, cramped, cold fortress, and it stank—the city had no sewers, and the accepted method of disposing of a night’s waste was to throw it into the street. The queen, who was not allowed to walk in public, breathed the street every night through her shutters.

She heard several masses a day. She collected relics. And above everything else, she was expected to produce a son. Within about six months of the wedding, she was pregnant.

On the 12th of July 1651, she gave birth to a girl, Margaret Teresa, the little child who stands at the center of Las Meninas. A girl was not what the king needed, but a living child was proof that the queen could produce one. After Margarita there was a long gap, four years of anxiety recorded in the king’s letters to a nun in a convent on the border of Aragon. Philip had been confessing his sins to Sor Maria de Jesus de Agreda for years, and the correspondence doubled as a running report on his efforts to get his niece pregnant.

Then in December 1655, Mariana gave birth to a second daughter, who lived fifteen days. The pressure on her was open by then. Philip was past fifty. He had no son.

On the 28th of November 1657, she finally produced one—Philip Prospero, a name that was a prayer. Madrid went insane with relief. The queen, meanwhile, was in serious trouble, developing childbed fever that nearly killed her. She was twenty-two.

She pulled through, probably in spite of the doctors rather than because of them. Philip Prospero was never well. He had violent epileptic seizures from infancy, and the whole apparatus of the court was turned toward keeping him alive. Velázquez painted him at about two, standing in a pink dress with amulets hanging from his sash—a bell to scare away the evil eye, a jet hand, an amber ball, small bags of relics.

Thirteen months later, Mariana had another boy, Ferdinand Thomas, so that for about ten months the king had a spare. Then the younger boy died, not yet a year old, in October 1659. Mariana was twenty-four and had now delivered four children and buried two. In the autumn of 1661, with his mother heavily pregnant again, Philip Prospero’s seizures got worse.

On the 1st of November, All Saints Day, one of them did not end. He died at three years and eleven months. Five days later, on the 6th of November 1661, Mariana gave birth to Charles. The palace had been hung with black for the prince; the black cloth came down off the walls and the bells rang the other way.

Philip wrote to the nun that God, who had taken one son with one hand, had given another with the other, and that he did not know whether he was supposed to weep or give thanks. The official gazette announced the new prince as a robust male, handsome of face, with black hair and somewhat pudgy. That was the public version. In private, the whispers started within weeks.

The imperial ambassador in Madrid received a letter from Vienna saying that people at the Austrian court did not believe Spain had a prince at all because the child was not male but female. Something about the baby’s genitals looked wrong to the people who had seen them. Louis XIV sent an envoy to have a look, and the report that went back to Versailles described a prince who seemed extremely weak, with both cheeks covered in a rash, his head covered in scabs, and an abscess behind his right ear draining onto his neck. Charles was never weaned.

He was still being breastfed at four years old when his father died, having gone through fourteen wet nurses—partly because the child bit. He could not stand unaided at three, when his skull had still not closed. He did not talk properly until around four. He was a physically wrecked child, and his mother’s entire political life would depend on keeping him alive.

Philip IV died on the 17th of September 1665. Ten days later, the greatest men in Spain knelt on the floor in front of a toddler who could not yet say his own name and put their lips to his hand, while Mariana stood behind the chair in her widow’s wimple. Somebody had to hold his arm out for him. The will named her regent with full royal authority until Charles reached fourteen.

It also pointedly left off the governing council the king’s eldest son, the only bastard Philip had ever recognized, Juan José de Austria. The king had trusted him with armies, but not with the boy. That guaranteed a fight, and the fight would be with Mariana. From that September until the day she died, she wore the dress of a widow: the white wimple bound close around the face, the black robe cut like a nun’s, the black veil down the back.

She looked, for the remaining thirty-one years of her life, exactly like a Franciscan nun. Spain in 1665 had declared bankruptcy four times in the previous twenty years. The army in Portugal was losing. The army in Flanders was unpaid.

And across the Pyrenees, Louis XIV was waiting. Mariana had been trained to pray and to produce heirs. Nobody had trained her to run this. She found a man to run it for her, choosing her confessor, an Austrian Jesuit named Juan Everardo Nithard who had been hearing her sins every day for sixteen years.

She had him made Inquisitor General of Spain, and within a year he was in everything but name prime minister. The old nobility took it as an insult delivered in person. The war with France went badly, the treaties that ended it were humiliations, and in 1668 a captain accused of plotting to murder Nithard was strangled in his cell without a public trial. It looked like a regent and her confessor strangling a man in the dark to protect themselves.

Juan José de Austria, watching from Aragon, started to move. In early 1669, he came down from Aragon at the head of a few hundred armed men and stopped just outside the capital. He did not need to attack. The city was with him, and even the council of Castile told the queen that the Jesuit had to go.

She held out for days and then gave in. On the 25th of February 1669, she signed the order, and two days later Nithard climbed into a coach and left Madrid for Rome with the crowd jeering him through the streets. He never came back. For Mariana, it was a public defeat and a private one.

She was thirty-four, with five years of regency left, and she had learned something about how power worked in Spain: a regent could not rule through a priest. Her next choice went worse, though not straight away. His name was Fernando de Valenzuela, a handsome nobody from Naples whose wife dressed the queen and who got access through her. He was clever, quick, fond of the theater, and within a few years he was the only man in Madrid the queen entirely trusted.

What caught everyone’s attention were the hours. The doors of the Alcazar were open to him at all times and by preference, and he came and went from her apartments after dark without being announced. Madrid gave him a nickname: the duende de palacio, the palace goblin. The court gossip was that the widow in the nun’s habit had taken a lover.

Whether the accusation was true, the evidence does not settle. She had been married at fourteen to a man of forty-four. He was charming and made himself indispensable. The court drew their conclusion.

His rise was absurd. He was made a knight of Santiago, given charge of the royal works and the royal theaters, made master of the horse. In 1675, he was made a grandee of Spain, the highest rank in the nobility, and in 1676 prime minister. The old families watched a man whose wife dressed the queen walk past them with his hat on his head.

Running under all this was the calendar. Charles turned fourteen on the 6th of November 1675, the day the regency ended under his father’s will. Mariana had the councils declare that the king’s health required a further period of regency. She bought herself two more years.

It cost her the boy. At fourteen and fifteen, Charles was a frightened child surrounded by people who told him he was being kept on a leash, that the goblin had his mother in his pocket, and that his big brother was waiting outside the capital to set him free. Whatever Mariana had been to him—and she had been everything—at fifteen, the boy chose the brother. On the night of the 14th of January 1677, the king was taken out of the Alcazar in secret and driven across town to the Buen Retiro, out of his mother’s reach.

He issued three orders. The first banished Valenzuela. The second summoned Juan José to court. The third instructed the Queen Mother to leave Madrid.

She was ordered to withdraw to Toledo, to a fortress on a hill forty miles south of the capital that had not been used as a residence in a generation. She was given two weeks. She left on the 2nd of March 1677, a woman of forty-two who had been regent of Spain since her son was three, sent away like a discarded mistress by a child she had nursed through every disease in the book. The ambassadors stopped coming.

The councils stopped sending her their paperwork. She heard mass, she wrote to Vienna, and she waited. Valenzuela fled to the Escorial and claimed sanctuary. A party of nobles dragged him out anyway, stripped him of everything, and shipped him off in chains to the Philippines, where he was held for a decade before being kicked by a horse in Mexico City and dying of it.

Juan José ran Spain for two and a half years. He was competent. He signed the peace at Nijmegen in 1678, giving Louis XIV Franche-Comté for good. He negotiated a wife for his brother, a French girl named Marie Louise.

And in the late summer of 1679, he fell ill with a fever that would not break and died on the 17th of September—the same date his father had died fourteen years earlier. He was fifty. Within days of the funeral, the eighteen-year-old king rode to Toledo in person and brought his mother back himself. She was forty-four.

She would never be regent again on paper, and she would never be out of the room again either. From that day until the day she died, she was the power behind her son’s chair, and everyone in Europe who wanted anything from Spain knew who to write to. The French bride arrived in November 1679. Marie Louise of Orléans was seventeen, had grown up in the most glittering court in the world, and had expected to marry her cousin and become queen of France.

Instead her uncle gave her to Spain, and she was sent south across the Pyrenees in a train of coaches, weeping. She had been told what she was marrying. The French ambassador had written that the Catholic king was so ugly as to cause fear. Charles was eighteen, thin, with the jaw so far forward that his mouth could not close over his teeth, drool at the corners of his mouth that had to be wiped.

He was, by every report, beside himself with excitement about the girl. Madrid then did to Marie Louise what it had done to Mariana thirty years earlier, only faster and with less patience. Her French servants were sent home, the etiquette wrapped around her, and the whole point of the marriage—an heir—was not happening. The French ambassador, wanting proof of the king’s fertility, bribed a palace laundry woman to bring him the king’s underwear and the queen’s bed linen so that he could examine the stains.

What the laundry showed, if anything, did not get written down. What did get written down was that the king of Spain could not father a child, and everyone who mattered in Europe knew it by the early 1680s. Marie Louise grew fat, ate from boredom and misery, developed a passion for a sweet drink that called for thirty-two pounds of sugar per batch, and began telling the few people she still trusted that she was afraid of being poisoned. She went riding on the 11th of February 1689.

By the afternoon she had a severe pain in the belly, low down on the right side; by evening she was vomiting violently. She died the next morning, so quietly her confessor wrote that they hardly noticed her go. She was twenty-six. Madrid said poison before the body was cold.

The court ordered an autopsy, which described a burst appendix and the peritonitis that followed it. It quieted nobody. Charles believed she was poisoned for the rest of his life. He was destroyed.

For weeks he would not be dressed. He shut himself in his rooms with the shutters closed, and he went across the Calle Mayor to his mother’s palace every day and sat with her for hours saying nothing. Mariana was fifty-four. She had lost her husband and four of her five children and been thrown out of her own capital.

She was the only person in Spain with the authority to make her son get back into a bed with a new wife. So she went looking for a replacement, and the replacement was chosen with a single criterion: breeding. She wanted a bride from a family that produced children the way orchards produce apples. She found one in the Palatinate.

Maria Anna of Neuburg was twenty-two, one of seventeen children, from a family that had not had a childless marriage in living memory and was reliably hostile to France. She was married to Charles by proxy in August 1689, six months after Marie Louise’s death, and arrived in person in May 1690. By the accounts from her first years in Spain, she was a hard and quick woman who took the measure of her husband within weeks and never afterwards pretended otherwise. One observer wrote that from the first she took charge and imposed her will on the king.

She had fits. When she was contradicted, she went into what the courtiers called hysterical crisis, screaming and collapsing until everyone around her went in mortal fear of setting one off. She faked pregnancies, several times announcing that she was expecting before the pregnancy quietly vanished. And she pushed her husband into the fertility treatments, the potions, and the exorcisms that this story came in on.

She and Mariana loathed each other. The queen mother had chosen this woman, brought her to Spain, and installed her in the Alcazar, and within a year the two of them were running rival factions in a court that could barely afford one. Mariana had the king’s heart. The wife had his bed, or what passed for it, and his fear.

For six years the palace was divided between an old woman in a nun’s habit and a young one who screamed, and the thin shaking man between them tried to please both and satisfied neither. What killed Mariana had probably been growing for some time before anyone knew about it. She had a lump in her left breast, and she would not let anyone look. She was sixty-one, had dressed as a nun for thirty years, and she was not going to let a man put his hands on her chest until she had no choice.

That moment came in the last week of March 1696. The physicians examined her, and on the 5th of April the senior court doctor wrote up what he had found. The tumor in the left breast, he wrote, was of the magnitude and size of the head of a newborn child. It was rooted in the ribs.

Its surface carried five or six excrescences hard as stones, and it was marked with livid spots. Its shape was irregular and horrible to see. The physicians would not cut. A mastectomy in 1696 meant a woman held down on a table while a surgeon took the breast off with a knife and a saw without anesthetic, and with a tumor rooted into the ribs there was nothing to cut it away from.

They chose what the record calls the preservative and palliative method: purges, bleedings, ointments, a diet. It did not stop. Over the next six weeks the medicines gave her fever and made her vomit repeatedly. The tumor kept growing.

It broke through the skin and ulcerated, an open weeping sore that bleeds and smells and has to be dressed several times a day. By May it was the size of the head of a seven-year-old child. The relics came. They brought her the body of San Isidro, the same incorrupt farmer they had carried to her husband’s deathbed thirty-one years before.

Fifty thousand masses were ordered for her soul. She died on the 16th of May 1696, at four to midnight, holding a crucifix that had belonged to Pope Pius V—the pope who had hesitated over the first Habsburg uncle-niece marriage 126 years earlier and granted it anyway. Her body was taken to the Escorial and put into a niche in the marble wall opposite Philip IV, who had been waiting there for her for thirty-one years. Before that, she went through the Pudridero, the rotting room, a plain chamber where the coffins of kings and queens were left sealed until what was inside had finished turning to bone.

Every Habsburg in the story went through that room. The stories started at once. A dove had been seen hovering over the body. A paralyzed nun was touched with one of the queen’s nightshirts and got up and walked.

When the doctors had opened her shirt to embalm her, the story went, the face of the corpse had suddenly reddened, and the surgeons had gone down on their knees. Her son believed them absolutely. The king collapsed. He took to his bed, would not eat, and had a run of seizures so severe that the ambassadors began writing home about the succession as though it were a matter of weeks.

Three years later, in the autumn of 1699, Charles took the Austrian ambassador down into the pantheon and had his mother’s coffin opened. He wanted the ambassador to look at her, to touch her, so that he could write to the emperor and report that the flesh of the queen mother’s face and hands was as intact as if she had died that morning. Harrach did as he was asked. What he actually saw, three years after burial in a stone crypt, in a body that had been opened and packed by seventeenth-century embalmers and had died with a rotting cancer in its chest, he was too polite to put in his dispatch.

He wrote that the king was much moved. With his mother gone, the king had nobody. His wife frightened him. His ministers were fighting each other over who would sell Spain to which foreign court once he was dead, and his body, which his mother had held together by force of will for thirty-four years, began to come apart in earnest.

By 1698, the French ambassador described him as so weak that he could not be out of bed for more than an hour or two. His feet, legs, belly, and face were swollen. His tongue occasionally swelled so badly that he could not speak. He was passing blood.

His seizures were more frequent and violent than ever. He was thirty-six years old. So in 1698 they tried the devil. The king’s confessor had heard of a convent in the mountains of Asturias where several of the nuns were possessed, and of a friar named Antonio Álvarez Argüelles who had a reputation as an exorcist.

Would he mind asking the devil whether the king of Spain had been bewitched, and if so, how and by whom? The answers came back over several months in letters dictated by demons speaking through the mouths of screaming nuns. Yes, the king was bewitched. It had been done through a cup of chocolate on the 3rd of April 1675, when he was fourteen.

The chocolate had contained the brain of an executed man, and his intestines, and his kidneys, and the spell had been made to take away the king’s reason and his health and his ability to father a child. The person behind it was the queen mother, so that she could keep power. You can see what that accusation was. April 1675 was the spring before Charles’s fourteenth birthday, the year Mariana had bent the councils to keep him under regency, the year the goblin was at the height of his power.

The nuns of Asturias, or the demons, or the friars putting words in their mouths, had picked the exact moment in Charles’s life when a court faction could most plausibly say that his mother had drugged him. Two years after she died in agony holding a crucifix, her son was told by the church that she had fed him a dead man’s brains to keep him stupid. He believed it, or believed enough of it to go through with the cure. The prescribed remedy was for the king to drink half a liter of holy oil on an empty stomach while the exorcisms were said over him.

He did. The vomiting and purging made him visibly worse. The exorcisms went on for the better part of a year until the king’s confessor was himself arrested and put on trial by the Inquisition for the crime of trying to cure the man he had been sent to save. In February 1699, Mariana’s great-grandson Joseph Ferdinand, the six-year-old Bavarian boy whom the powers of Europe had more or less agreed on as the heir to Spain, caught smallpox and died.

With the child gone, the succession came down to a straight choice between a French grandson of Louis XIV and an Austrian grandson of Mariana’s brother, and every party in Madrid took a side, and the dying king was pulled between them like a rope. Through the summer and autumn of 1700, Charles was dying, and everybody knew it. The rest of Europe had known it since his cradle. On the 3rd of October 1700, he signed his last will, naming Philip of Anjou, the seventeen-year-old grandson of Louis XIV, heir to the whole of the Spanish Empire.

He is reported to have wept over it. He died on the 1st of November 1700, All Saints Day, the same day of the year on which his brother Philip Prospero had died in a seizure thirty-nine years earlier, five days before his own birth. He was five days short of thirty-nine. The surgeons opened him the day after he died.

The report has come down to us in several versions that agree on the essentials. The corpse, they wrote, did not contain a single drop of blood. The heart was the size of a peppercorn. The lungs were corroded.

The intestines were rotten and gangrenous. He had a single testicle, black as coal, and his head was full of water. Three large stones were found in the kidneys. What it describes in terms a doctor would use now is a man who had been in heart failure for years, with fluid on the brain, chronic kidney disease, a bowel destroyed by a lifetime of purges and infection, and genitals that had never properly developed.

The single black testicle answers the question that the letter from Vienna had asked in the first weeks of his life. What had been born in 1661 was a boy, but only just, and never one who could have fathered anybody. The war started within months. Philip of Anjou was proclaimed in Madrid in November.

The Austrian claimant refused to accept it, and by the summer of 1701 the armies were moving. It ran for thirteen years and killed, by the usual estimates, somewhere over a million people. When it was done, the Bourbons had Spain and the Habsburgs had lost it. The house that had married its own nieces to keep the blood pure had bred itself out of existence in the person of a man with a peppercorn for a heart.

Mariana is still in the marble wall at the Escorial in the black habit, across from the uncle she married at fourteen. The islands in the Pacific still carry her name. The portrait of the teenage queen is in the Prado, a few rooms away from the painting of her little daughter in the white dress, and the later portraits of the widow, folded hands, white wimple, black veil, hang near them, so that you can walk from one to the other in about a minute and cover forty years.