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Princess Alexandra of Bavaria -

The German princess was convinced she swallowed an entire glass grand piano as a child, and that any sudden movement would break the instrument.

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Louis XIV -

King Louis XIV of France had a thing for enemas, an injection of fluids into the lower bowel via the rectum. The fluid would often be scented with rose, bergamot, and angelica.

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Charles VI of France -

After having suffered from a strong fever and convulsions, the French king developed paranoia and violent rages that made him dangerous. Charles was also another royal who believed he had glass in his body. When the delusion was at its strongest, he would sit for hours without moving.

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Qin Shi Huang -

Perhaps China’s most influential ruler, Qin Shi Huang was a Qin dynasty emperor who famously built the Terracotta Army. He became obsessed with immortality.

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Ivan IV -

The first tsar of a centralized Russia, Ivan IV, also known as Ivan the Terrible, truly lived up to his nickname. The tsar caused his kingdom great terror, and left most of those around him executed.

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Peter I -

Also known as Peter the Great, the Russian tsar implemented a "beard tax" in an attempt to mirror Western Europeans. He lined up his staff and the Russian military and shaved all their faces.

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Caligula -

Known for being an insane tyrant, Caligula believed he was a living god and forced his people to worship him as such. When Romans had enough of his insanity, they stabbed him to death. 

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Zhengde -

Emperor of the Ming dynasty from 1505 to 1521, Zhengde installed eunuchs in all positions of his government. They handled governing matters, and he was able to devote his life to pleasure-seeking.

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Maria Eleonora of Brandenburg -

A German princess who later became queen of Sweden, Maria Eleonora of Brandenburg tried on several occasions to kill her only child, Christina, as she couldn't provide the king a male heir. Also, when her husband King Gustavus Adolphus died, she refused to bury his body for a year, and slept below a hanging casket that contained his heart.

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George III -

King of England and Ireland, George III is believed to have suffered from various mental ailments brought on by a hereditary blood disorder called porphyria. In his later years, he would have severe violent episodes, which forced his staff to put him in a straight jacket.

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Nabonidus -

According to the biblical Book of Daniel, Nabonidus, the king of Babylon, came down with a seven-year spell of madness. He retreated from society and lived like an animal.

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Joanna of Castile -

Also known as Joanna the Mad, she was the Queen of Castile from 1504, and Queen of Aragon from 1516 to her death in 1555. She earned the title of "mad" due to her obsession with her husband. She even kept his deceased body next to her at all times.

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Ibrahim I -

Sultan of the Ottoman Empire, Ibrahim I came into power after the death of his brother in 1640. A mad ruler, he had his entire harem drowned.

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Ludwig II of Bavaria -

The German king spent most of his reign building fairy-tale castles. One of his most famous is Neuschwanstein Castle, which today is a popular tourist attraction.

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Catherine II -

Commonly known as Catherine the Great, the Russian empress helped turn Russia into one of the great powers of Europe. However, her personal life was a bit more controversial. It was rumored that she had a long list of lovers, which may even have included a horse!

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Paul I -

The Russian tsar was an eccentric character who was obsessed with the uniforms his royal guards wore. He would also throw unnecessary military parades for his own entertainment.

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Henry VIII -

The English king used to make noblemen kiss his bed in case it had been poisoned. He was even more paranoid for his son, Edward, and forbade him from wearing new garments brought straight from the tailor.

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Peter III of Russia -

Catherine the Great’s husband, Peter III didn't match her drive and intellect. They didn't get along, and it's even unclear whether they ever consummated their relationship. Instead, he was known for playing with toy soldiers in bed.

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Erik XIV -

Erik XIV of Sweden was once a charming prince, until his paranoia developed into schizophrenia. The disorder caused him to have violent rages that even ended in murder.

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Elagabalus -

Probably one of Rome's most vicious, self-indulgent, and cruel rulers of all time, Elagabalus' has an endless list of evil acts. One notable perversity of his was when he tied dinner guests to a water wheel and watched them slowly drown.

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Crown Prince Sado -

Born in 1735, the Korean prince suffered brutal treatments at the hands of his father, King Yeongjo of Joseon. This turned him into a cruel and violent human who would have people killed on a daily basis. He was obsessed with alcohol, which was illegal at the time, and even tried to seduce his younger sister. He was locked up when his fathered discovered some of his deeds. Sado starved to death behind bars.

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George IV -

Before becoming King of Great Britain and Ireland, George IV had accumulated a lot of debt and illegally married a Catholic woman. He formally married his cousin, Caroline, whom he hated and went to great lengths to keep from being crowned queen.

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Isabella I -

Not so long ago, hygiene was not as important as it is today, and the Catholic Church even claimed bathing was a sin practiced by the pagans. Therefore, it's not a surprise that in the 15th century, Queen Isabella of Spain bragged that she had only bathed twice in her whole life.

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Rudolf II -

The Roman emperor was an eccentric figure who was known for being a patron of the arts, sciences, and pseudo-sciences. As a ruler, he would often go weeks without speaking to the court. Instead, he spent his time supporting astrologers and alchemists.

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Christian VII of Denmark -

Even with childlike behaviors, Christian VII became king of Denmark at the age of 17. Frequently caught pleasuring himself, doctors at the time deemed him as unhealthy. Today, it's believed that he was either schizophrenic or bipolar.

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Vlad III -

Born in 1431 in what is modern-day Transylvania, Vlad III loved to impale his enemies, which is where he got his nickname, Vlad the Impaler. Dracula, the fictional character, created by author Bram Stroker, was based on him.

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Mustafa I -

Before becoming Sultan of the Ottoman Empire, Mustafa I lived a life behind bars. This was because he wasn't first in line to the throne. His older brother, Ahmed I, became sultan in 1603, and according to Ottoman tradition Mustafa had to be executed to prevent him from attempting to supplant his brother. However, Ahmed spared his life, and held him captive in a window-less prison. Incarcerated for 14 years, Mustafa then took the throne after his brother's death. But due to years being locked up, he had gone mad and was replaced by his nephew.

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Nero -

The fifth emperor of Rome, Nero was a complete narcissist who had his own mother killed. He also married a random man who looked like his second wife, whom he murdered. The man was forced to dress in female clothes and act like a woman.

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Justin II -

Ruler of the Byzantine Empire from 565 to 578 BCE, Justin II was so mad that he would bite others in the court. He also demanded that organ music be constantly played to calm him down. 

Sources: (Ranker) (History) 

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