The vision inside the Tattered Spire is nothing more then a teaser for what is to come within the Fable world, whether this refers to more Fable II content or Fable 3 is unknown, it has been said in an interview that Lionhead Studios are not finished with Fable II yet and its also been reported that Fable 3 is in Pre-Production. So nobody knows just yet what Aurora is, but is more then likely to be known with the arrival of Fable 3. However fans have had their say on the matter and some people think it could be a person, or others believe that it could be where the next Fable is set. So unfortunately, you will have to wait and find out, whatever you read at this point on this subject is pure speculation.