I reread (well, re-listened, actually) Peace Talks and Battle Ground recently, and I don't think it's ever explained where they came from. A mortal had to summon them, right?
Except they're the Dresden Files iteration of the Hounds of Tindalos, which are creatures that find and hunt you when you mess with the fabric of time.
So, questions:
1. If they were summoned, who summoned them? Again, it needs to be a mortal practitioner. Could it have been Justine? My understanding is that magic was necessary to summon an Outsider, and Justine isn't magically talented. Justine is the obvious answer, particularly because they were attacked right as Harry left. But Justine needs Harry to take her to the Island, so why risk that he'd be torn to pieces?
2. Was there time travel during the events of Peace Talks and Battle Ground? I find it intriguing that it was specifically Cornerhounds who were summoned. Why those particular types of Outsiders rather than any of the others we've seen? They weren't especially effective at attacking Eb and Harry. Were they intended to fail, or were they following their instincts to attack time travelers?
Like I said, it's entirely possible the answer is simple "Justine, duh," but I think there's some room for debate here. Anyone have any thoughts?