Rome's emperor Nero has long been written off as mad. Yet, there has been a misreading of his intelligent, and eccentric ways. He inherited the throne after the death of Claudius and at first, he seemed to offer Rome some stability. But he was a ruthless man. He murdered his stepbrother and rival for the throne Britannicus. He also had two of his three wives murdered, one of whom he kicked to death himself. And that's not all, he also crafted the horrendous murder of his own mother. Though, some of the stories about him have been regarded as suspect because of the hostility towards him of many ancient writers.
While most of his predecessors and successors made their name on the battlefield, Nero's interests were cultural and artistic. He had a skill for writing poetry and playing the lyre and would openly parade his artistic side, forcing senators to sit for hours during his dramatic performances. He had also introduced a poetry competition into the Olympic Games so that he could win it.
But perhaps, Nero's eccentricity came about due to his alleged theatrics, since there were claims that he sang and played the lyre while watching the spectacle of the city of Rome ablaze. However, this is almost certainly untrue. Nero may have possibly remarked on the spectacle, but rather, he seems to have in fact been directing the firefighting rather than rhapsodizing. Nevertheless, since he built a massive Golden House for himself in the middle of the area of destruction, so perhaps bad press after the event was only to be expected.
After a long conflict with England - the Hundred Years' War - Charles VI had inherited the throne. He had come to the throne as a minor and had been kept out of power until he reached the age of 20. As a young man, he seemed able and popular. But in 1392, while on campaign in the forest of Le Mans, he had some sort of seizure that had badly affected his mind, causing him to violently attack his companions. He killed four of them.
From that point on he was subject to periodic fits of violence while his everyday behavior became all the more bizarre. He used to run wildly through the corridors of his palace and seemed unaware of his own name. Once, he appeared to claim to be Saint George. The king suffered from delusion. He believed that he was made of glass and could shatter at any time. At the time of his death in 1422, it was a large relief for all concerned. The throne was then passed to Henry V's infant son, Henry VI.
Rudolf II, Holy Roman Emperor, Archduke of Austria and King of Hungary and Bohemia, was viewed by some as a maligned figure, a true Renaissance patron of the arts. But in his lifetime, he was regarded as dangerously insecure. In fact, he was overthrown and replaced by his own brother. This was the period of religious conflict between Catholics and Protestants, in which Germany had been deeply divided between the two camps. But, by the time of Rudolf's accession, a compromise peace was successfully at work.
While Rudolf was a staunch Catholic like the rest of the Habsburg clan, his spiritual life was further fueled by an increasingly absorbing interest in the occult and a strong sense of paranoia. He was prone to bouts of what today would be recognized as mood swings and depression and shut himself away in his Prague Castle. During such times, he refused to see or speak to anyone for days on end. The Habsburg family was alarmed that Rudolf's impulsiveness might tear the empire apart. So they engineered a palace coup that put Archduke Matthias on the imperial throne instead of his brother. This served, however, to increase the violence of Rudolf's persecution complex.
While it may be that Rudolf has been unfairly judged, his behavior did seem dangerously erratic to those around him. In addition, it sowed the seeds for the disastrous Thirty Years' War (1618-48) which engulfed Europe six years after Rudolf's death.
Many rulers may have been driven over the edge into mental instability due to the stifling nature of life and deadly power struggles in Constantinople's Topkapi Palace. This was certainly the case of Mustafa I, who was twice briefly the Sultan of the Ottoman Empire in the early 17th century. It was normal practice for an incoming Sultan to have all his brothers put to death to avoid any possibility of their claiming the throne. But this did not happen to Mustafa when his elder brother Ahmed I came to the throne in 1603. This was likely because Ahmed had felt some affection for his brother and likely because there was no alternative direct heir. Regardless, Mustafa's behavior seemed to suggest that he was a harmless eccentric. Like many other rulers, he developed a high degree of paranoia and he also had no desire to rule.
When Ahmed died in 1617, Mustafa succeeded mainly because no-one could agree on another candidate. He is described as having enjoyed teasing the viziers, knocking off their turbans or pulling at their beards. Other rulers have behaved in a similar fashion in history, but they had been strong enough to get away with it. In Mustafa's case, it undermined his fitness to rule. Consequently, after just a year as sultan, he was overthrown by his nephew Osman II. But Osman was also overthrown and murdered in a palace coup by the Janissaries, the palace guard. At which point, Mustafa was restored to the throne.
This unexpected turn of events seemed to have disturbed Mustafa's mind. He had convinced himself that Osman II was still alive, but he was hiding. So he spent hours looking for him in cupboards and dark corners. In the end, Mustafa was removed from the throne with the agreement of his mother.
This queen was something of a celebrity in her time and was most certainly regarded as eccentric. She proved to be irresistible to opera composers, dramatists, and romantic novelists. Her father, King Gustavus Adolphus, triumphantly led the Protestant princes in battle against the Holy Roman Empire until he was shot in the head at the 1632 battle of Lützen. His grieving widow would not allow his body to be buried. From time to time she would open the coffin to see how her late husband was decomposing.
Christina succeeded to the throne and she immediately attracted comments due to her rejecting all the behavior that was expected of a queen. She was also determined not to marry because her own sexual orientation probably ran in the other direction. She enjoyed dressing in men's clothes, which at the time was seen as eccentric and as a rejection of the laws of God.
She was a great patron of the arts, commissioning paintings and welcoming writers, so that Sweden, became, for some time, a major center of European learning. In addition, she was unconventional in her approach to politics too, undermining her own chancellor, Oxenstierna, in the peace negotiations at the end of the Thirty Years' War. In 1654 Christina suddenly abdicated. It is possible that she had suffered some sort of breakdown. So, she retired to Rome. Still, her arrival was anything but low key. She arrived in full state, dressed as an Amazon. She was welcomed, primarily because she was a prominent royal Protestant who had converted - that was something of a rarity. She was eventually buried there.
Peter the Great of Russia was a man of enormous dynamism and energy. But, he was also a very dangerous man to cross. His behavior is one that can be described as unpredictable and eccentric. He came to the throne having narrowly escaped with his life from the deadly intrigues at the Romanov court. It may, therefore, be that this awareness of the fragility of his royal existence affected his behavior.
During his stay in England, he lodged in the Thameside house of the diarist John Evelyn, where he and his friends trashed the place using pictures for pistol practice and covering the floors in vomit and urine. He showed a similar lack of concern for the sensitivities of his subjects. And he encouraged the nobles to abandon their traditional dress and adopt western styles. In fact, he had them lined up and cut off their beards himself. He punished revolt and defiance with mass executions, which he was happy to start with his own hands.
Peter was a great builder. He ordered the construction of the city of St Petersburg and he didn't worry too much that building it on a marsh would inevitably cause the deaths of thousands of laborers. Perhaps, his reign pushes the definition of eccentric rather too close for comfort to the homicidal autocrat.