I have not dealt with that, yet, in my writings, but I plan to do so. The same answer, and I have not dealt with this yet, but hopefully will deal with this in one more book, is the question of their return, which, of course, has many facets. This is a whole vast subject, and I have come up with a certain amount of answers. As you know, I try to base my writings on what I call facts - in other words, data from antiquity, rather than just speculation. There's no point in speculating.
People write books in which they speculate.
Then, they are writing fiction. I am writing nonfiction. So, these are valid questions. I have collected some special amount of data about them. I am not satisfied, yet, with the data.