How did Iblis know that Adam and his descendants would descend to Earth, while he had not yet descended, so as to say to Allah Almighty: "He said, 'My Lord, because You have put me in error, I will surely make [what is in] the earth attractive to them and I will surely mislead them all'"?

Iblis knew that Adam and his descendants would descend to Earth after Allah informed the angels that He was going to place a vicegerent on Earth. Iblis himself alluded to this, saying: ﴿He said, "My Lord, because You have put me in error, I will surely make [adornments] pleasing to them on earth and I will surely mislead them all."﴾