What does Mark 13:21 mean?

Preterists believe that all biblical prophecy—or most, for partial preterists—was fulfilled as of the destruction of Jerusalem in AD 70. Futurists believe that although some prophecy may have more than one meaning, end-times predictions will not happen until the end times. Mark 13:21–22 seems to refer to human history from the point of Jesus' ascension on, although, as with all other hardships, it is commonly believed things will get worse as Jesus' second coming grows nearer.

False teachers have plagued the church since its inception. Dozens, from the mentally ill to the opportunistic, have claimed to be Jesus. Some deceived over a million followers and others manipulated their followers into killing themselves in the hope of salvation.

The deception will grow worse in the end times. When the sun and moon grow dark and the waters turn to blood and the world is covered with plagues, famines, and war, the unscrupulous will take advantage of the suffering. Currently the Holy Spirit is keeping evil spiritual forces from developing into the ultimate manifestation of the Antichrist. In the end times, His restraining hand will be lifted, giving Satan his chance to rule the world, but also allowing lesser, human, deceivers the freedom to take what they can (2 Thessalonians 2:7). Unbelievers who know a little of what the Bible says about Jesus will easily believe that someone else with magical powers (Mark 13:22) will rescue them.

Jesus' second coming will not be so subtle. After the tribulation, when the sun, moon, and stars are dark, Jesus will appear "in clouds with great power and glory" (Mark 13:26), and the people of the earth will mourn (Matthew 24:30). Revelation describes Jesus as riding a white horse and making war, with eyes of flame and a robe dipped in blood (Revelation 19:11–13). This is a far cry from a cult leader who suggests that worship includes giving him your money and having sex with him.