Just started reading Jeremy Duff's book Peter's Preaching, an exploration of the message of Mark's Gospel. Duff suggest that Mark is trying to pass on Peter's message and is not interested in writing a chronologically ordered diary. He takes various themes, starting with the theme of being a disciple.
Duff suggests that Jesus gives the 'Twelve', the core group of disciples, three roles - "to be with him, to proclaim the message and to have authority over demons."
Duff recognises that we might prefer something more 'mainstream' than having authority over demons. However he suggests that "It is perhaps appropriate and helpful to see 'authority over demons' as equivalent to 'authority to release people from whatever binds them.'"
I certainly find that helpful. As we read the pages of the Gospels, we indeed see "Jesus bringing this release to people". What a great mission in which to share!