Explanation: Caligula was a Roman Emperor who began with a promising and mild reign once he ascended to the position of Emperor!

Unfortunately, after an illness and fever so high it put him into a coma for several days, he woke up... worse. Much worse. And he proceeded to get worse every day for the rest of his reign. Threats, murder, arbitrary executions, seizures of property, delusions of godhood... Caligula did whatever pleased his fancy on any given day, and it was rarely a good fancy.

It's speculated by some modern historians that the fever caused brain damage and a loss of impulse control.