Who or what are moon children?
A year or so before the beginning of World War I, a young woman named Lisa la Giuffria is seduced by a white magician, Cyril Grey, and persuaded into helping him in a magical battle with a black magician and his black lodge. Grey is attempting to save and improve the human race and condition by impregnating the girl with the soul of an ethereal being the moonchild. To achieve this, she will have to be kept in a secluded environment, and many preparatory magical rituals will be carried out. The black magician Douglas is bent on destroying Grey's plan. However, Grey's ultimate motives may not be what they appear. The moonchild rituals are carried out in southern Italy, but the occult organizations are based in Paris and England. At the end of the book, the war breaks out, and the white magicians support the Allies, while the black magicians support the Central Powers.: Moonchild
So as I would put it, a Moonchild is a child spawned during a Satanic ritual, with the intent of opening a gateway to demonic influence through the child via the fact that both parents are acting under demonic influence at the time of conception (sort of an attempted perversion of the Incarnation, just as the Black Mass is a perversion of the Mass). L. Ron Hubbard famously tried to create a Moonchild during an OTO ritual while he was associated with Parsons and Parsons' wife, which Crowley mentioned in a letter after he heard about it. Q may be adding something to Crowley's original concept--sounds like Q and some sites commenting on Q might be proposing there's some identifiable lineage of Moonchildren, which would be a new one for me.