zavladati

1. (of a mood, silence, trend) to set in; to take hold; to prevail
   Kada je ušao, u sobi je zavladala tišina. — When he walked in, silence fell over the room.
   Posle vesti gradom je zavladala panika. — After the news, panic gripped the city.
2. (+ instr.) to take control of; to come to rule
   Posle kraljeve smrti zemljom je zavladao njegov sin. — After the king's death, his son came to rule the country.
   Rimljani su zavladali celim Balkanom. — The Romans took control of the entire Balkans.

What is ruled or taken over goes in the instrumental: zavladati zemljom, zavladala je gradom.