Answer
Boris Godunov, the Tsar's brother-in-law and a powerful boyar, effectively wielded power in Russia during the rule of Tsar Feodor I, who was known for his weak health and limited involvement in governance. Godunov's influence stemmed from his familial connection to the Tsar, his political acumen, and administrative skills. He addressed internal challenges and established diplomatic ties, shaping Russia's trajectory during Tsar Feodor's reign.