He murdered his heir in a fit of rage, which ultimately led to the end of the Rurikid dynasty and the beginning of the Time of Troubles with the ascension of his son Feodor.
This overthrower of the khanates of Kazan and Astrakhan divided lands under his control into zemshina and created a standing army called the streltsy. This ruler called the first zemsky sobor, or "assembly of the land," in his country. His person army of men on black horses was called the oprichniki. He murdered his heir in a fit of rage, which ultimately led to the end of the Rurikid dynasty and the beginning of the Time of Troubles with the ascension of his son Feodor. For 10 points, name this fearsome Grand Prince of Moscow.
This overthrower of the khanates of Kazan and Astrakhan divided lands under his control into zemshina and created a standing army called the streltsy.
Ivan IV [or Ivan the Terrible; or Ivan Grozni; prompt on Ivan]