Ivan the Terrible
Ivan was born in 1530CE and, 3 years later, he inherited the throne on his father's death. His mother, who acted as his regent and who had had Ivan's uncle arrested and imprisoned for challenging her son's right to succeed, died (of poison) when he was 7. After her death, Ivan was abandoned and ignored by much of his nobility, as boyar families feuded over power and possessions. At the age of 13 Ivan rebelled against this anarch, and ordered one of the soi-disant Princes thrown to a pack of hounds. The rule of the boyars had ended.
He was crowned tsar at 17 and he married three weeks later, to the winner of a national virgin competition. Anastasia was the daughter of a minor noble and they were close. On her death, in 1560, Ivan's somewhat extreme nature sprang into full bloom, as he accused his nobles of having murdered her. He was to marry a further 6 times, but found all his later wives too "whorish" and either exiled them to church dungeons or simply ordered their execution.
Prior to her death he had ruled strongly and well: the printing press was introduced into Russia, the law code was revised, a standing army established, a council of nobles formed, and the church was reduced to a subordiate position against the civil state. He also strengthened trade links and oversaw the construction of Saint Basil's Cathedral in Moscow. Less foresightedly, he introduced the first laws restricting the movement of peasants, which would eventually lead to a system of serfdom.
Ivan also saw himself as Russia's Crusader, principally against the Muslim Tartars, against whom he waged a mericless series of campaigns.
In 1574 Ivan left Moscow for his palace in Alexandrov, and named Simeon Bekbulatovich, a baptised Tartar khan, as Grand Prince of all Russia. Simeon ruled from Moscow for between 2 and 3 years, and was then married to Ivan's cousin and made the ruler of the areas of Tver and Torzhok, whilst Ivan resumed his duties as Tsar.
During this period of his life Ivan became paranoid for his own safety and created a 'secret police' -- the Oprichinki -- a brotherhood dedicated to the safety and well-being of the Tsar. He had long suspected the boyars of continued disloyalty, not least when, in 1553, they refused to swear allegiance to his son Dimitri, when Ivan fell ill. There are also indications that he became unbalanced, vacillating violently between wild depravity and extreme piety over a matter of days. He gave orders for atrocities and massacres, and then made elaborate penance for his cruelty. It was during this period that he beat his daughter-in-law for immodesty and then accidentally killed her husband, his son Ivan. Three years later Ivan himself was dead, very probably poisoned with mercury (possibly in the wake of an allegation he had tried to rape a noble's daughter), and the throne passed to his childless son, Feodor. On his death-bed Ivan embraced the monastic life and was re-christened as the monk Jonah.