User blog comment:Omega natsu2/Chapter 387: Tartarus Arc, Part 4: Father and Son, Predictions./@comment-24784846-20140530224650/@comment-7418318-20140531145857

That was the case, but I don't think that stands in the way of the theory.

He could have summoned Deliora from nearby to his town, rather than from the book into reality. Or simply attracted the attention of the Demon by dabbling in the magic, which resulted in Deliora altering its path to lead it to Gray's home.