Howling:The nightmare child

I believe the nightmare child is a construct not a living being(This is speculation)as in a prop review of the history of the time war book used in journey to the center of the tardis there is a picture of the jaws of the nightmare child and it resembles a massive stone construct energy coming out of a split between one of the arms wich could be "it's jaws" what it does I have no theories-Zachary