Most significantly of all, what is Ashildr doing watching Clara from the gates of Coal Hill School? Whereas she might have had contact with other former companions, Clara is someone she has met before in the Viking village and knows that the Twelfth Doctor is current travelling with across time and space. Is she protecting Clara from the Doctor? Does she know Clara's eventual fate? Or is there some aspect of jealousy? The Doctor refused to take Ashildr with him but with Clara out of the way, he might change his mind. Is she somehow linked to what will happened to Clara at the end of series nine? It all depends on whether she is good or bad...