And there is the answer to who played a big role in the ritual. Even though this was probably not done deliberately, Maester Aemon had always helped Jon Snow, and the sagely old man was infinitely better compared to that old bastard Dumbledore. Even in death, he was able to help him. Sadly, he couldn't do anything to heal his sister, so he'd have to get the next best thing. Woods witches from beyond the wall had plenty of hands-on experience with dealing with wounds and were probably the only people who had any idea about non-magical healing in the near vicinity.