Lying in someone's power represents being controlled or ruled by him. Alternate translation: "the whole world is controlled by the evil one" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "world" represents all the people who rebel against God. Alternate translation: "all the people of the world are under the power" (See: [[rc://en/ta/man/translate/figs-metonymy]])