Peter Capaldis Doctor is a being who recognizes his place as the trickster of the universe but isnt happy about it. He is the instigator of the action, a driving force for change. He is not a savior though those around him persist in perceiving him that way. The Doctor arrives at places in time that need a nudge in the right direction. He lives his life as a perpetual tipping point, as if he were created to keep various forces in check or risk the universe slipping into chaos. This is the second time weve had mention of a hybrid. Is Ashildr somehow part of the prophecy spoken of by Davros in The Magicians Apprentice? Its interesting to note that River Song might also be termed a hybrid and is returning in the Christmas special. There have been allusions to River sprinkled throughout series nine. In this episode the Doctor speaks of draining Ashildr like a battery which is also how River met her end in Forest of the Dead.