For 10 points, name this first Russian ruler to have the title of Tsar, a man infamous for his ruthlessness.
This ruler provided aid to Yermak after Yermak conquered the khanate of Sibir, and this man convened the first Zemsky Sobor. This ruler was defeated by Stephen Bathory in the Livonian War, and he founded a secret police force called the (*) oprichina. This Rurik dynasty ruler killed his namesake son in a rage in 1581, and he was succeeded by his advisor Boris Godunov. For 10 points, name this first Russian ruler to have the title of Tsar, a man infamous for his ruthlessness.
This ruler provided aid to Yermak after Yermak conquered the khanate of Sibir, and this man convened the first Zemsky Sobor.
{Ivan IV} [or {Ivan} the {Terrible}]