Ghasts are the noisy undead that are similar to ghosts. Unlike ghosts, ghasts are only the evil spirit of their physical host that has already moved on, caused by their host, in life, doing a tragic thing or the way they died, so they cannot move on. Ghasts are harmless unless if someone is afraid of them. The local spook, John Gregory, said that they cannot move on by giving them a good talking, but they can still move on, which was proven when Mam went up to Hangman's Hill and the moans grew quieter to help Tom Ward finally sleep. However, it is still unknown how she did this, and we may never know due to her death. After a while, unless they moved on previously, ghasts will naturally move on.