One of the fortresses on the route north from Molthune, which protects the roads that supply the crusade, is attacked in the dead of night by kind of a lot of vampires and their even more numerous thralls. The hope must have been that the fortress wouldn't successfully get a Sending off, but they do, and very shortly after that the Knight-Commander is there in person along with half a dozen other people who eat vampires for snack.
Or maybe that was the hope, because shortly after she arrives there's an extraordinarily powerful magical discharge of some kind, and they lose half the fortress wall, and Iomedae (winged, in pursuit of some vampires) is suddenly -