1. adds force to a statement, decision or conclusion; indicates command
at sentence end
痛いなら寝てていいぞ。If it hurts, you can stay in bed.
2. (strongly) emphasizes the previous word; adds focus
3. some- (e.g. something, someone)
after an interrogative
今頃どこぞに閉じこもって震えていることだろう。By now they're probably holed up somewhere, trembling.