Board Thread:Whoniverse Discussion/@comment-24121492-20150912163108/@comment-24121492-20150917063520

Turtlecake365 wrote: I did see the prequel and it seems/hoping there will be another prequel as the pics released for the prequel were not in the one that we actually got. I think it has something to do with the Dalek city with the Doctor having to face his biggest challenge yet and he is referring to the snake monster which is the Human with lines all over his face when he says old friend. I seen the other prequel as well. Someone recorded it and posted it in the comments on /r/gallifrey.

Also, the scar man is on Karn in the trailer, so he must know that the Doctor went there somehow.