... Also very intrigued by that child-like figure. It's not the boy, it's yet another representation of Casca, and I think it's one that's hiding itself. It's "the thing in the Abyss of Casca", as the text says.
Hey Aaz! I haven't seen this discussed since this particular mention, but I wanted to discuss this idea further. Specifically, why you don't think it's the moonlight child.
Before I continue, I think the child being a representation of casca makes the most sense. But just for discussions sake: looking at the sketches, with the way the chatacter is shown, it reminds me a lot of past instances when the moonlight child kind of just "shows up"/appears/whatever the correct term is. Also, we have seen the child come to guts' aid when he was in trouble, in astral form; is it a farfetched idea that he would show up to help casca, too?
Having this discussion/asking this question of you based off of sketches alone is more than likely moot, especially (as you've stated) with this being casca's deep conscious, the childlike figure being her makes the most sense. If it is the moonlight child, however, I think that would definitely add another element to this moment (not like it needs it