Satan is the mystery of iniquity. -> Who he was. -> Who he now is. -> Why he rebelled. -> What his plan is
Michael (see comment on 2Th 2:6) is ^he who now lets^ contending with Satan and keeping him from unleashing the fulness of his raw evil.
When Michael is taken out of the way Rev 12:7-10 Satan will incarnate himself in the beast, the AntiChrist.
At that point, he will manifest lying wonders with which to deceive the whole world.