*Spoilers*
So, after listening to the book a second time, something occurred to me. If this has been brought up before, please let me know.


So, what I am thinking is...when it was time for Harry and Justine to leave for the Island, Harry made a point that he wasn't going to walk there (the Beach, where the Blue Beetle is docked), understandable for what he went through the past few hours... so he ends up riding Mab's personal Steed and focus of Magic, much like his own staff. Along with Justine. We know Harry's Starborn status protects him from Nemfection...so him being so close to Justine by riding horse back, not a big deal.

But what about the Steed itself? If Cat Sith, Lea, Maeve, Aurora, and a dagger could be infected, I don't see why a unicorn couldn't, and thus spread its infection into Mab. I don't know about you guys, but Mab becoming Nemfected? That sort of screams "Apocalypse", especially since a nemfected Mab (Nab?) could just open the outer gates.