By stating this in a negative form Paul is emphasizing that the Corinthians should expect to meet many "false apostles" ([2 Corinthians 11:13](./12.md)). AT: "we should expect this ... We should certainly expect that" (See: [[rc://en/ta/man/translate/figs-litotes]])
"Light" often is used as a metonym for "righteousness" or even "God." AT: "Satan disguises himself as an angel of righteousness." (See: [[rc://en/ta/man/translate/figs-metonymy]]).