There aren't any others as of now and Nosferatu is the only one, but I think Vincent said he found an empty file in the code for tomes with the name "Mire". Considering Witches are DLC and they get shadowgift I'm going to go out on a limb here and say maybe the dlc they come with might come with mire or maybe some other dark tomes. I mean it seems like they aren't hesitant at all about throwing new items and stuff in through the dlc this time around. As we can see from those seals that promote people into Lucina's or Marth's class.