Since you had brought up mother dearest (who I can now say with even more certainty is not getting any parents’ day gift just like the father):
The mother’s mark and overall reaction to Caleb’s claim to seeing a hobgoblin has actually raised great number of suspicions on her from my end…since it seems she may be a lot more aware of the mythological world than she wants to let at the moment.
There was something odd about the way she kept adamantly denying the idea that Caleb. It wasn’t like how a parent dents the existence of the Easter Bunny or Santa: it was as though she wanted to do everything she could to deny the idea of something mythological was at play, to the point of being willing to blaming Caleb. She claims it’s because she truly believes Caleb had caused that action, but I currently don’t buy that (Feels like she has a little more awareness than the father in a sense).
And the whole affair thing seems to be heavily implied at this point even on the mother’s end, so it seems there is a good of truth on the father’s end on that matter. Playing River (who leans heavily on the Stoic side) they actually took note of a lacy unmentionable that was trying to be hidden amongst their mother’s work blouses. And that clearly is something of significance for the mother, since she seemed kind of reactive to the fact that her child clearly took note of that. But here’s the thing: we have yet to figure out why she’s having a affair in the first place. Heck, that magic mark of hers has honestly made me wonder if she’s actually doing this affair to gain some magic related benefit…one that harbors more of cost than a crumbling marriage and disintegrating relationship with her children…if she even has any actual care toward them anymore (Gotta admit, I LOVE how little River could coldly remark that their mother had no right to play the parent card when she was barely around to be a parent to begin with; loved the way the mother was actually stunned silent. Though Duran having the guts to declare that he knew Caleb better than his own mother at that point was an equally great steam release). Again though, that currently makes her actions even worse: because that mean she’s VERY much willing to sacrifice a number of things in her life to gain something she feels is completely worth those losses (if that’s even the reason she’s having a affair to begin with).
Also just putting this out there but…in number of fantasies, runes are often etched on to the skin in a way that seems similar to that of a tattoo. And we know that Luis apparently has a good amount of knowledge of runes himself. Just something to think about.