Here "lead many astray" is a metaphor "persuades many to believe what is not true." Alternate translation: "deceive many people" (See: [[rc://en/ta/man/translate/figs-metaphor]]]])
This is metonym. Possible meanings are 1) Alternate translation: "claiming my authority" or 2) Alternate translation: "claiming that God sent them." (See: [[rc://en/ta/man/translate/figs-metonymy]])