The source of Jesus' power is brought into question. Jesus confronts them with the nature of his mission to push back and overthrow evil. Jesus had come to crush and bind Satan for the kingdom of God to be ushered in.
Jesus begins to establish The Kingdom of Heaven. The Gospel of Mark begins Jesus ministry with Him laying the foundation of the good news of the kingdom. This was the dawn of the new age of God fulfilling His promises through the promised Messiah.